Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, Second Part: Subclass Osculosa; Index
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Title: Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, Second Part: Subclass Osculosa; Index
Author: Ernst Haeckel
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Transcriber's note:
Text enclosed by underscores is in italics (_Actissa_).
The underscore also denotes a subscript, so _c__1 is an
italic c with a subscript (note that there are two
underscoreds between the "c" and the "1").
Text enclosed by hash marks is in "gesperrt"
(wide-spaced) type (#Larcoidea#).
Page numbers enclosed by curly braces (example: {25}) have
been incorporated to facilitate the use of the Index.
Some typographical errors in the printed work have been
corrected. They are listed at the end of the text.
The Addenda & Errata (Second Part, pp. 1763-4) have been
applied without further comment.
REPORT ON THE SCIENTIFIC RESULTS OF THE VOYAGE OF H.M.S. CHALLENGER
DURING THE YEARS 1873-76
Under the Command of Captain George S. Nares, R.N., F.R.S.
and the Late Captain Frank Tourle Thomson, R.N.
Prepared Under the Superintendence of
the Late Sir C. Wyville Thomson, KNT., F.R.S., &c.
Regius Professor of Natural History in the University of Edinburgh
Director of the Civilian Scientific Staff on Board
and Now of
John Murray
One of the Naturalists of the Expedition
ZOOLOGY--VOL. XVIII.
SECOND PART
Published by Order of Her Majesty's Government
Printed for Her Majesty's Stationary Office
and Sold by
London:--Eyre & Spottiswoode, East Harding Street, Fetter Lane
Edinburgh:--Adam & Charles Black
Dublin:--Hodges, Figgis, & Co.
1887
Price (in Two Parts, with a Volume of Plates) £5, 10s.
CONTENTS.
REPORT on the RADIOLARIA collected by H.M.S. CHALLENGER during the years
1873-1876.
By ERNST HAECKEL, M.D., Ph.D., Professor of Zoology in the University of
Jena.
SECOND PART.--OSCULOSA.
(#NASSELLARIA AND PHÆODARIA.#)
CONTENTS.
SECOND PART.
II. Subclass OSCULOSA, 889
Legion III. NASSELLARIA vel MONOPYLEA, 889
Order 11. Nassoidea, 895
" 12. Plectoidea, 898
" 13. Stephoidea, 931
" 14. Spyroidea, 1015
" 15. Botryodea, 1103
" 16. Cyrtoidea, 1126
Legion IV. PHÆODARIA vel CANNOPYLEA, 1521
Order 17. Phæocystina, 1542
" 18. Phæosphæria, 1590
" 19. Phæogromia, 1642
" 20. Phæoconchia, 1710
Note on the Dimensions and Measurements, 1760
ADDENDA, 1761
ERRATA, 1763
INDEX, 1765
{889}LEGION III. NASSELLARIA,
VEL MONOPYLEA, VEL MONOPYLARIA (PLS. 51-98).
_Nassellaria_ (_inclusis_ Spyridinis), Ehrenberg, 1875.
_Monopylea_, Hertwig, 1879.
_Monopylaria_, Haeckel, 1881.
_Cyrtida_ et _Acanthodesmida_, Haeckel, 1862.
_Cricoidea_, Bütschli, 1882 (L. N. 40, p. 537) = NASSELLARIA.
_Definition._--Radiolaria with simple membrane of the central capsule,
which is monaxon or bilateral, and bears on one pole of the main axis a
porous area (porochora), forming the base of a peculiar intracapsular cone
(podoconus). Extracapsulum without phæodium. Skeleton siliceous, very
rarely wanting. Fundamental form originally monaxon, often dipleuric or
bilateral.
The legion NASSELLARIA vel MONOPYLEA, in the extent here defined, was
constituted in 1879 by Richard Hertwig in his work Der Organismus der
Radiolarien (pp. 133-137). He gave to this large group the rank of an
order, and united in it the two families Acanthodesmida and Cyrtida, which
I had constituted first in 1862 in my Monograph (pp. 237, 265, 272); but he
added, too, as a third family the Plagiacanthida, united by me with the
former. In the first system of Ehrenberg (1847, _loc. cit._, pp. 53, 54),
four families belonging to the MONOPYLEA were enumerated, the
Halicalyptrina, Lithochytrina, Eucyrtidina, and Spyridina. He united the
three former under the name "Polycystina solitaria," which he afterwards
changed into NASSELLARIA (1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p.
157).
In my Monograph of the Radiolaria (1862, pp. 265-345) forty-four genera of
NASSELLARIA were enumerated (six Acanthodesmida and thirty-eight Cyrtida),
whilst the total number of genera in the whole class of Radiolaria at that
time amounted to one hundred and thirteen. But owing to the astonishing
number of new and interesting forms of this legion which I afterwards
detected in the collection of the Challenger, in 1881 I distinguished in my
Prodromus not less than three hundred and seventeen genera. These were
disposed in five large main groups, retained in the present Report, with
twenty-six families, viz., (1) #Plectoidea# (with three families), (2)
#Stephoidea# (with four families), (3) #Spyroidea# (with four families),
(4) #Botryodea# (with three families), and (5) #Cyrtoidea# (with twelve
families). The first two groups have an incomplete or rudimentary skeleton,
and may be united in the order #Plectellaria#, whilst the other three
families possess a complete latticed shell, and {890}may be united as
#Cyrtellaria#. The former correspond to the Acanthodesmida, the latter to
the Cyrtida in my Monograph.
The character common to all MONOPYLEA or NASSELLARIA, which separates them
from all other Radiolaria, was first recognised by Richard Hertwig in 1879,
and consists in the singular structure of the monaxonian central capsule,
bearing on the basal pole a peculiar porous area or operculum, the
"Porenfeld;" we call it shortly the "porochora." It represents a circular
or elliptical porous plate on the basal pole of the vertical main axis of
the central capsule, and bears a peculiar "podoconus" or
"Pseudopodien-Kegel," a conical body of singular structure, protruding
inside the membrane into the capsule. The pseudopodia arising from this
peculiar "podoconus" proceed from the capsule piercing the "porochora,"
whilst the other parts of the capsule are not perforated.
The MONOPYLEA are therefore "Merotrypasta," like the following fourth
legion, the PHÆODARIA or CANNOPYLEA. But in these latter we find on the
basal pole of the monaxonian capsule only one single large main opening,
prolonged into a peculiar tube, and there is no trace of the typical
"podoconus," characteristic of all NASSELLARIA. The latter agree, however,
with the former in the possession of a basal opening, serving for the
emission of the pseudopodia, and in the monaxonian fundamental form,
arising from this structure. Therefore these two legions of "Merotrypasta"
exhibit a wider divergence from the ACANTHARIA and SPUMELLARIA, the two
legions of "Holotrypasta," in which the central capsule is everywhere
perforated by innumerable small pores (compare above, pp. 5, 6, 716).
_The Skeleton_ in all NASSELLARIA consists either of pure silica, or of a
peculiar silicate; never of acanthin (as in all ACANTHARIA). The siliceous
bars and beams constituting it are invariably solid (as also in the
SPUMELLARIA); never hollow (as in the PHÆODARIA). In the small family of
Nassellida alone (with the two genera _Cystidium_ and _Nassella_) the
skeleton is entirely absent. In all other genera of NASSELLARIA the
siliceous skeleton is more or less developed; imperfect, or quite
rudimentary in the #Plectellaria# (#Plectoidea# and #Stephoidea#), but
perfect and forming a regular lattice-shell in the #Cyrtellaria#
(#Spyroidea#, #Botryodea#, and #Cyrtoidea#). The different forms of this
skeleton exhibit an extraordinary variety, but may be reduced to a few very
simple fundamental forms, or even to a single, most simple original form.
The comparative morphology is more interesting, but also more difficult to
understand than in any other Radiolaria.
The geometrical fundamental form of the skeleton is in all NASSELLARIA
monaxonial, the vertical main axis of the body, which is already indicated
by the axis of the central capsule with two different poles, being also
expressed constantly in the form of the skeleton. The lower or basal pole
of the latter always exhibits a different shape from that of the upper or
apical pole. This difference is so striking in nearly all MONOPYLEA, that
the two poles may be determined on the first view.
{891}In the great majority of NASSELLARIA not only is the monaxonial
fundamental form expressed, but also the dipleuric or bilateral, so that
the symmetrical halves of the body may be easily determined; the right and
left halves exhibit the same symmetry as in the vertebrates, so that we may
distinguish an anterior ventral and a posterior dorsal face of the body.
The whole form is in this case determined by three dimensive axes,
perpendicular to one another, two of which are heteropolar, the third is
homoeopolar. The apical pole of the vertical main axis (principal or
longitudinal axis) is different from the basal pole. The ventral pole of
the horizontal sagittal axis (or dorso-ventral axis) is different from the
dorsal pole. The right pole of the horizontal transverse axis (lateral or
frontal axis) is equal to the left pole. Therefore the sagittal or median
plane of the body (in which the principal and the sagittal axis are
crossed) divides it into symmetrical equal halves and is perpendicular to
the frontal axis.
Three different original elements of structure are recognisable in the
majority of NASSELLARIA, viz., (1) a vertical simple ring, the primary or
sagittal ring, placed vertically in the sagittal plane and enclosing the
median plane of the central capsule; (2) a basal tripod, composed of three
diverging radial rods, which are united on the basal pole of the central
capsule and are either expanded horizontally or descend; (3) an ovate or
subspherical, simple lattice-shell, the cephalis or capitulum, which
surrounds the central capsule and exhibits a peculiar structure on its
basal pole.
These three important original elements of structure--the sagittal ring,
the basal tripod, and the latticed cephalis--are so united in the majority
of NASSELLARIA that the cephalis rests upon the tripod and includes the
sagittal ring wholly or partially. The simplest realisation of this typical
union is afforded by the Archiperida and Tripospyrida, and these may be
derived from the simpler important Stephanid _Cortina_ (Pl. 83, fig. 9; Pl.
92, fig. 21; Pl. 97, fig. 1). In this and in all other tripodal
NASSELLARIA, the three basal rods or the "cortinar feet" are constantly so
arranged that an odd or posterior rod, the "caudal foot" (_c_) is opposed
to the two anterior paired rods, the "pectoral feet" (one right, _p_", and
one left, _p_'). The caudal foot lies in the sagittal plane, and is
prolonged upwards into the dorsal rod of the sagittal ring (_b_), and over
this in a free ascending spine, the "apical horn" (_a_). The curved ventral
rod of the ring (_r_) is united above with the base of the apical horn,
below with the common centre of the tripod or the "cortinar centrum." The
characteristic position of the central capsule in this skeleton of
_Cortina_ is such that its basal pole (with the porochora) rests upon the
centre of the tripod, whilst its sagittal perimeter is separated from the
surrounding ring by the calymma; the numerous pseudopodia arising from its
base diverge downwards and are supported and protected by the three basal
feet of the tripod (Pl. 97, fig. 1). Compare also Pls. 51, 53, 84, 95, 98.
The typical skeleton of _Cortina_, a tripodal ring, becomes more developed
in the Semantid _Cortiniscus_, in which the basal parts of the three
diverging feet are united {892}by a second horizontal ring, the cortinar or
basal ring (Pl. 92, figs. 11-13). The pores between the former and the
latter, or the "cortinar pores," may be regarded as the first beginning of
the lattice-plate, composing the "cephalis" or the simple primordial shell
in the Archiperida and Tripospyrida, and transmitted from these by heredity
to the great majority of NASSELLARIA.
The "cephalis or capitulum" (the "Köpfchen" of the German authors) is
therefore the most important part of the skeleton in all #Cyrtellaria#, or
in all NASSELLARIA possessing a complete lattice-shell. In the
#Plectellaria#, however, or in those NASSELLARIA which do not possess a
complete fenestrated shell, the "cephalis" is either imperfect or totally
wanting. The cephalis surrounds the enclosed central capsule on all sides
in the form of an ovate or subspherical lattice-shell, and is separated
from it only by the jelly-like calymma. The sagittal ring is either
enclosed in the wall of the cephalis (whole or partially), separating its
two lateral halves, or it is enclosed in the cavity of the cephalis and
connected with its sagittal perimeter by short beams. The base of the
cephalis (with the cortinar plate) often rests immediately upon the centre
of the tripod; in the majority of NASSELLARIA, however, this near relation
is altered by reason of later changes and secondary modifications.
The number of various forms, developed from these simple original
structural elements of the skeleton, is astonishing, and there are
described more than three hundred genera and nearly two thousand species of
this legion in the following pages. This large number may be easily
increased by subsequent observers. Since in all these MONOPYLEA the
characteristic structure of the central capsule is identical, and also the
structural elements of the siliceous skeleton are similar, it is very
probable that they may have arisen from a single common stock. But it is
very difficult (and at present impossible) to explain a natural
monophyletic system of this large legion. The greatest difficulty is
presented by the fact that the three structural elements mentioned above,
viz., the sagittal ring, the basal tripod, and the latticed cephalis, are
not constantly united, but each alone may also constitute the skeleton by
itself. In this respect the following seven cases are possible, and are
actually realised.
A. The skeleton is composed of the sagittal ring only and of its spiny
appendages, without basal tripod and without latticed cephalis. This is the
case in the majority of #Stephoidea# (Stephanida, Semantida, Coronida, and
Tympanida).
B. The skeleton is composed of a basal tripod only (_Plagiacantha_), or of
a tripod in the centre of which arises a vertical apical horn
(_Plagoniscus_), and often of an irregular framework, arising from the rods
of the tripod; but there is neither a trace of a sagittal ring nor a
complete latticed cephalis. This is the case in the remarkable suborder
#Plectoidea# (Plagonida and Plectanida).
C. The skeleton is composed of a latticed cephalis only, a simple ovate or
subspherical fenestrated shell, which encloses the monopylean central
capsule; there is no {893}trace of a sagittal ring nor of a basal tripod.
This is the case in the remarkable family of Cyrtocalpida (Archicorida and
Archicapsida), in numerous #Botryodea# and in other #Cyrtellaria#.
D. The skeleton is composed of a sagittal ring and a basal tripod, without
latticed cephalis. This is the case in a few, but very important forms of
#Stephoidea#: _Cortina_, _Stephanium_, _Cortiniscus_, _Stephaniscus_,
_Podocoronis_, and some allied genera.
E. The skeleton is composed of a sagittal ring and a latticed cephalis, but
without basal tripod. This is the case in numerous #Cyrtellaria#, in the
Circospyrida (or Zygospyrida apoda: _Dictyospyris_, _Circospyris_) and some
other #Spyroidea#; and in a large number of #Botryodea# and Cyrtoidea
eradiata (a part of the Sethocyrtida, Theocyrtida, Lithocampida, and
others).
F. The shell is composed of a basal tripod and a latticed cephalis, but
without any trace of the sagittal ring. This is the case in numerous
Cyrtoidea triradiata and multiradiata, and perhaps in the majority of the
following families--Tripocalpida, Tripocyrtida, Podocyrtida, and
Podocampida.
G. The shell is composed of all three above-mentioned elements, of a
sagittal ring, a basal tripod, and a latticed cephalis. This is the case in
the great majority of #Spyroidea# (with a few exceptions only), and perhaps
also in the majority of #Cyrtoidea#.
The survey of these seven groups, A to G, each of which is represented by
numerous living forms, shows clearly how difficult and complicated the
morphology and phylogeny of the numerous NASSELLARIA must be. For all
possible combinations of the three original structural elements are
realised abundantly, and in such complicated relations, and so intermingled
in the different orders and families, that it seems nearly hopeless to
answer the question of their true origin. The identity in the structure of
the central capsule, however, in all these MONOPYLEA, makes it probable
that they have all arisen originally from the skeletonless Nassellida
(_Cystidium_, _Nassella_), either in a monophyletic or in a polyphyletic
way. In this respect the following phylogenetical hypotheses are possible.
1. Monophyletic hypothesis, deriving all NASSELLARIA from a simple sagittal
ring (_Archicircus_, _Lithocircus_, &c., Pl. 81). The groups A, D, E, and G
may be derived easily from such a ring, but the groups B, C, and F only by
means of the hypothesis that the original ring may be completely reduced
and finally lost. This hypothesis was stated by me in the years 1877 to
1879, when I had got the first general survey of the astonishing number of
new NASSELLARIA in the Challenger collection, and as I had found the
sagittal ring in the majority of them. This, my former hypothesis, is
mentioned by Richard Hertwig (1879, _loc. cit._, pp. 68, 126). It was
afterwards supported with particular energy by O. Bütschli (1882, Zeitschr.
für wiss. Zool., Bd. XXXVI.).
2. Monophyletic hypothesis, deriving all NASSELLARIA from a basal tripod
(_Triplagia_, _Plagoniscus_, &c., Pl. 91). The groups B, D, F, and G, all
triradiate, may {894}be derived easily from such a tripod; but the groups
A, C, and E only by means of the hypothesis that the original tripod may be
completely reduced and finally lost. This hypothesis was employed in 1881
in my Prodromus, since I had convinced myself that the "triradial
structure" is prevalent in the great majority of NASSELLARIA, and is
perhaps more important than the sagittal ring.
3. Monophyletic hypothesis, deriving all NASSELLARIA from a latticed
cephalis, a simple ovate or subspherical fenestrated shell without ring and
tripod (_Cyrtocalpis_, _Archicapsa_, &_c._). The groups C, E, F, and G may
be derived easily from such a cephalis, but the groups A, B, and D only by
means of the hypothesis that the sagittal ring as well as the basal tripod
may remain as the last remnants of a reduced cephalis. This hypothesis was
given in 1862 in my Monograph, where I constructed the first pedigree of
Radiolaria (p. 234). I there derived all the Cyrtida from the #Sphæroidea#
(_Cyrtidosphæra_), supposing that _Cyrtocalpis_ and some other Monocyrtida
may form a direct phylogenetical passage from the #Sphæroidea# to the
#Cyrtoidea#.
4. Polyphyletic hypothesis, deriving the different groups of NASSELLARIA
from different skeletonless Nassellida, by development of simple siliceous
skeletons in different ways. Among the numerous polyphyletic hypotheses
which are possible, one of the simplest would be the supposition that three
different fundamental forms of skeleton may have arisen independently one
from another: (1) a simple sagittal ring as original form of the
#Stephoidea# and #Spyroidea# (A); (2) a simple basal tripod as original
form of the #Plectoidea# (B); (3) a simple latticed cephalis as original
form of the #Botryodea# and #Cyrtoidea# (C). This triphyletic hypothesis is
supported by R. Hertwig (1879, _loc. cit._, p. 136); he assumes that the
original skeletonless Nassellida (_Cystidium_) have produced three
different branches, his "Acanthodesmida" (= #Stephoidea# and #Spyroidea#)
with a primary ring, his "Plagiacanthida" (= #Plectoidea#) with a primary
tripod, and his Cyrtida (= #Botryodea# and #Cyrtoidea#) with a primary
cephalis. This hypothesis seems rather probable on the first view; but it
meets with the greatest difficulties in view of the fact that these three
original elements of the skeleton are more or less evidently combined in
the great majority of NASSELLARIA. The greatest difficulty arises from the
fact that often among very similar and closely allied forms the first
exhibits all three elements (A, B, C) combined, whilst the second has a
combination of A and B, the third of B and C, the fourth of A and C; and
there are other forms, very similar to the former, in which one element
only is recognisable. Another difficulty arises from the fact that the
intimate structure of the cephalis in the majority of #Cyrtellaria# is not
perfectly known, and often exhibits structures which are difficult to
explain with regard to the three elements A, B, C. Under these
circumstances further researches on the numerous imperfectly known
NASSELLARIA are required, and chiefly accurate observations on their more
minute structure and on their important ontogeny.
{895}We divide the immense legion of NASSELLARIA into two large orders, the
#Plectellaria# without complete lattice-shell, and the #Cyrtellaria# with a
complete lattice-shell or a "cephalis," including the central capsule; the
latter, of course, have arisen from the former. The #Plectellaria# comprise
three different suborders, the #Nassoidea# (without skeleton), the
#Plectoidea# (with a tripodal skeleton, without ring), and the #Stephoidea#
(with a primary sagittal ring, with or without tripod). The #Cyrtellaria#
again also comprise three different suborders, the #Spyroidea# (with
bilocular cephalis and a sagittal constriction), the #Botryodea# (with
multilocular and lobate cephalis, exhibiting two or more constrictions and
three or more lobes), and the #Cyrtoidea# (with simple, unilocular
cephalis, without constriction).
_Synopsis of the Orders and Suborders of_ NASSELLARIA.
I. Order {No skeleton, 1. #Nassoidea#.
PLECTELLARIA. {
Nassellaria without {Skeleton with a basal tripod,
complete lattice-shell. { without ring, 2. #Plectoidea#.
{
{Skeleton with a sagittal ring
{ (usually without tripod), 3. #Stephoidea#.
{Cephalis bilocular, with a
{ sagittal constriction, 4. #Spyroidea#.
II. Order {
CYRTELLARIA. {Cephalis multilocular, with
Nassellaria with a { two or more constrictions
complete lattice-shell. { and lobes, 5. #Botryodea#.
{
{Cephalis simple, without
{ constriction and lobes, 6. #Cyrtoidea#.
----
Order V. PLECTELLARIA, Haeckel, 1883.
_Definition._--NASSELLARIA without complete lattice-shell, usually with an
incomplete skeleton, formed of a ring, a tripod, or an irregular framework.
Suborder I. NASSOIDEA, Haeckel.
_Definition._--NASSELLARIA without skeleton. Single family Nassellida.
{896}Family XLV. #NASSELLIDA#, Haeckel.
_Cystidina_, Haeckel, 1883, Sitzungsb. Jena Ges. für Naturw., Februar 16.
_Definition._--NASSELLARIA without skeleton. The soft body composed of a
monopylean central capsule (with porochora and podoconus) and of a
surrounding jelly-veil or calymma.
The family #Nassellida# comprises the simplest and most primitive forms of
NASSELLARIA, the only group which is entirely without a skeleton. The
central capsule is therefore perfectly free and naked, enveloped by the
calymma only, as in the #Colloidea# among the SPUMELLARIA, in the
Phæodinida among the PHÆODARIA. Probably these naked and skeletonless
MONOPYLEA must be regarded as surviving remnants of the common ancestral
group of this legion; but the possibility is not excluded that the few
observed forms are either young NASSELLARIA which have not yet secreted a
skeleton, or older NASSELLARIA which have lost their original skeleton.
We distinguish in this small family two genera only: _Cystidium_ with
hyaline, not foamy calymma, without extracapsular alveoles, and _Nassella_,
with a very voluminous foamy calymma, including numerous large alveoles;
the former corresponds to _Actissa_ and the latter to _Thalassicolla_ among
the #Colloidea# or the skeletonless SPUMELLARIA. But in these two latter
genera, as in all PERIPYLEA, the central capsule is perforated everywhere
by innumerable small pores; the two former genera, however, exhibit the
same characteristic podoconus in the central capsule, and the same
porochora at its base, as all the other MONOPYLEA. The pseudopodia are
protruded from the central capsule through the porochora only.
_The Central Capsule_ is in the two observed genera either ovate or nearly
spherical, usually slightly tapering towards the basal mouth. Its
transverse section is constantly circular. The membrane of the capsule is
usually rather thick and double-contoured, and bears on the truncate basal
pole a circular "porochora" or area porosa, through which the pseudopodia
are protruded. The _porochora_ is either quite simple, circular, or in some
species trilobed, with three equal circular lobes, each of which is
surrounded by a girdle of small granules. The _podoconus_, or
"pseudopodial-cone," arising vertically from the horizontal basal
porochora, is half as long as the central capsule, or longer, simply
conical and finely striped longitudinally. The _nucleus_ lies usually in
the uppermost part of the central capsule, above or behind the podoconus,
and is either spherical or ovate, sometimes kidney-shaped. It includes one
or more nucleoli.
_Synopsis of the Genera of Nassellida._
Calymma hyaline, without alveoles, 382. _Cystidium_.
Calymma foamy, with numerous large alveoles, 383. _Nassella_.
{897}Genus 382. _Cystidium_,[1] R. Hertwig, 1879, Organismus d. Radiol., p.
87.
_Definition._--#Nassellida# with hyaline calymma, without extracapsular
alveoles.
The genus _Cystidium_ is the simplest and most primitive among all
NASSELLARIA, and may be regarded as the common ancestral form of this
legion, for which it has the same high importance as _Actissa_ for the
SPUMELLARIA. The central capsule is quite simple, ovate or nearly
spherical, and included in a voluminous hyaline calymma, which contains no
large alveoles. _Cystidium_ differs from _Actissa_, its probable ancestral
form, in the possession of the "podoconus" and its basal "porochora,"
characteristic of all NASSELLARIA or MONOPYLEA.
1. _Cystidium princeps,_ n. sp. (Pl. 91, fig. 1).
Central capsule ovate, one and a third times as long as broad. Podoconus
with simple circular porochora, about half as long as the capsule,
surrounded at its base by red granules of pigment. Nucleus spherical. Three
equal oil-globules in the endoplasm. No pigment in the voluminous calymma,
which includes numerous xanthellæ.
_Dimensions._--Length of the central capsule 0.1, breadth 0.075; nucleus
0.035.
_Habitat._--Indian Ocean, Maldive Islands (Haeckel), surface.
2. _Cystidium lecythium,_ n. sp.
Central capsule ovate, one and a half times as long as broad. Podoconus
with simple circular porochora, three-fourths as long as the capsule.
Nucleus ellipsoidal. No oil-globules in the endoplasm. No pigment and no
xanthellæ in the calymma.
_Dimensions._--Length of the central capsule 0.12, breadth 0.08; nucleus
0.04.
_Habitat._--Central Pacific, Station 271, surface.
3. _Cystidium inerme,_ R. Hertwig.
_Cystidium inerme,_ R. Hertwig, 1879, Organismus d. Radiol., p. 87, Taf.
vii. figs. 1-1_b_.
Central capsule subspherical, a little longer than broad. Podoconus about
two-thirds as long as the capsule, with trifid porochora, which is composed
of three equal circular lobes. Nucleus spherical. Numerous oil-globules in
the endoplasm. The calymma includes numerous xanthellæ and brown pigment
around the mouth.
_Dimensions._--Length of the central capsule 0.06, breadth 0.05; nucleus
0.03.
_Habitat._--Mediterranean, Messina (R. Hertwig), surface.
{898}Genus 383. _Nassella_,[2] nov. gen.
_Definition._--#Nassellida# with foamy calymma, containing numerous large
extracapsular alveoles.
The genus _Nassella_ differs from the preceding _Cystidium_, its probable
ancestral form, in the development of numerous large alveoles in the
extracapsular calymma, and therefore exhibits the same relation to it that
_Thalassicolla_ bears to _Actissa_ among the SPUMELLARIA. The foamy calymma
is very voluminous, and includes numerous symbiotic xanthellæ.
1. _Nassella thalassicolla_, n. sp.
Central capsule spherical. Podoconus with simple circular porochora, half
as long as the capsule. Nucleus spherical. Numerous oil-globules in the
endoplasm. Calymma spherical, without pigment, with numerous xanthellæ and
large alveoles.
_Dimensions._--Diameter of the central capsule 0.12, nucleus 0.04, calymma
0.6.
_Habitat._--South Pacific, Station 300 (off Juan Fernandez), surface.
2. _Nassella nassiterna_, n. sp.
Central capsule ovate. Podoconus two-thirds as long as the capsule, trifid,
with three equal circular lobes (as in _Cystidium inerme_). Nucleus ovate.
Three equal large oil-globules in the endoplasm, corresponding to the three
lobes of the porochora. Calymma ovate, in the upper half much more
voluminous than in the lower, including numerous large alveoli and
xanthellæ, and around the mouth masses of black pigment.
_Dimensions._--Diameter of the central capsule 0.1, nucleus 0.03, calymma
0.8.
_Habitat._--Indian Ocean, Madagascar (Rabbe), surface.
----
Suborder II. PLECTOIDEA, Haeckel.
_Plectoidea_ vel _Plectida_, Haeckel, 1881, Prodromus, p. 423.
_Plagiacanthida_ (_sensu ampliori_), R. Hertwig, 1879, Organismus d.
Radiol., p. 72.
_Definition._--NASSELLARIA with a rudimentary, originally tripodal
skeleton, composed of radial spines, arising from one common central point
or central rod; the spines are simple or branched, and the branches may
form by concrescence of their meeting ends a loose wickerwork, but never a
complete lattice-shell. Never a ring in the skeleton.
{899}The suborder #Plectoidea#, hitherto known by few species only of
"Plagiacanthida," comprises a large number of interesting NASSELARIA, which
belong partly to the simplest and most primitive forms of this legion. It
may be divided into two different families, Plagonida and Plectanida. In
the first family, Plagonida, the monopylean central capsule is supported by
a simple or rudimentary skeleton, composed only of a variable number of
radial spines united in a common centre. In the second family, Plectanida,
the branches of these radial spines become united and form a loose
irregular framework with wide meshes, partly enclosing the central capsule,
but never a perfect lattice-shell.
The #Plectoidea# differ from the following suborder, the #Stephoidea#, in
the absence of the ring, characteristic of the latter. Some slight traces,
however, indicate a near affinity between the ringless #Plectoidea# and the
ring-bearing #Stephoidea#. Both these suborders of #Plectellaria# differ
from the closely allied #Cyrtellaria# (#Spyroidea#, #Botryodea#, and
#Cyrtoidea#) in the absence of a complete lattice-shell. The morphological
relation and phylogenetic affinity between the former and the latter have
already been discussed in the preceding description of the legion
NASSELLARIA (compare pp. 891-894).
The first known species of #Plectoidea# was observed in the North Atlantic
(on the Norwegian shore) in 1855 by my late friend Edouard Claparède, and
described and figured in his Études, &c. (1858), under the name
_Plagiacantha arachnoides_. He considered it as a new genus of
Acanthometrina. Another species, from the Mediterranean, was described in
the same year by Johannes Müller as _Acanthodesmia dumetum_ (1858, _loc.
cit._, Taf. i. fig. 3). A third species, also Mediterranean, was figured by
me in 1865 under the name _Acanthodesmia polybrocha_. Finally, Richard
Hertwig, 1879, in his Organismus der Radiolarien, gave a very accurate
description of another Mediterranean form, _Plagiacantha abietina_ (_loc.
cit._, Taf. vii. fig. 6). He first recognised the true character of
MONOPYLEA in their monaxonian central capsule, and observed at the same
time the first NASSELLARIUM without skeleton, called by him _Cyrtidium
inerme_ (_loc. cit._, Taf. vii. fig. 1). To these four known species,
representing three different genera, the rich collection of the Challenger
has added so many new forms that we may distinguish here not less than
seventeen genera and sixty-one species. In my Prodromus (1881, p. 423) I
arranged these in two subfamilies, the Plagonida and Plectanida,
constituting together the family Plectida (identical with the
"Plagiacanthida" of Hertwig and Bütschli). But at present, regarding the
important relations of these Plectida to the other NASSELLARIA, it seems
more convenient to give to them the rank of an independent suborder of
Radiolaria, under the name #Plectoidea#.
The peculiar structure of the central capsule of the #Plectoidea#, first
recognised by Richard Hertwig, allows no doubt of their being true
MONOPYLEA or NASSELLARIA; and also their siliceous, originally triradiate
skeleton indicates the nearest affinity to {900}the other families of this
legion. But a very difficult and as yet unsolved problem is the important
question, in what manner these different groups of NASSELARIA are
phylogenetically connected. Either the #Plectoidea#--as the simplest of
all--are the original common ancestral group of this whole legion (as I
assumed in my Prodromus, 1881), or they are derived from the #Stephoidea#
(by reduction of the sagittal ring), or they have originated independently
from them (if we suppose a polyphyletic origin of the MONOPYLEA. Compare
above, p. 893, &c.). In any case the typical "triradial structure" of the
#Plectoidea#, prevalent also in the other groups of this legion, is a very
important and interesting fact.
The triradial skeleton of the #Plectoidea# exhibits in the two families of
Plagonida and Plectanida a complete homology of development, so that each
genus of the latter may be derived from a corresponding genus of the
former, simply arisen by concrescence or union of the branches of the
radial spines. Therefore the only difference between the two closely allied
families is, that the branches of the radial spines in the Plagonida remain
free, whilst in the Plectanida they produce a loose framework or wickerwork
by union of their meeting ends. We express this complete homology in the
nomenclature of the #Plectoidea#, in each genus of Plagonida retaining the
syllable "Plag-"; in each genus of Plectanida, correspondingly, the
syllable "Plect-."
The number of radial spines composing the skeleton is originally three, and
in all not triradial genera is probably derived from three. For better
survey we may divide each family, according to the different number of
rays, into four different subfamilies: A, with three radial spines
(Triplagida and Triplectida); B, with four radial spines (Tetraplagida and
Tetraplectida); C, with six radial spines (Hexaplagida and Hexaplectida);
and D, with numerous (seven to nine or more) radial spines (Polyplagida and
Polyplectida). The last three subfamilies have arisen probably from the
first triradial subfamily, by a secondary increase in the number of rays.
The important signification of the triradial structure, recurring in the
most different groups of NASSELLARIA, has been already pointed out
sufficiently by myself and by R. Hertwig. But the triradial #Plectoidea#
offer also another interesting relation of this characteristic structure,
some simple forms of this order appearing nearly identical with the
isolated triradial spicula of certain #Beloidea# (Thalassosphærida and
Sphærozoida). Even some more complex quadriradial and sexradial forms of
the latter reappear in exactly the same shape also in the former. This
identity may be perhaps an important indication of true affinity (compare
below).
The simplest and probably the most original kind of triradial structure is
exhibited by the genera _Triplagia_ and _Triplecta_ (Pl. 91, figs. 2, 7).
Here three equal radial spines lie in one horizontal plane and are united
in a common central point at equal angles, so that three lines connecting
their distal ends form a regular equilateral triangle. Simple triradial
spicula of the same regular form are also found in many {901}#Beloidea#
(_Lampoxanthium_, _Sphærozoum_, &c., Pls. 2 and 4). The central capsule of
these simplest #Plectoidea# (with vertical main axis) rests perpendicularly
on the horizontal triangle, formed by the triradial skeleton; the porochora
of the former (or the "area porosa") rests upon the central point of the
latter.
Another kind of triradial structure characterises the genera _Plagiacantha_
and _Plectophora_. The three radial spines united in the central point lie
here not in one plane, but diverge in different planes, so that they
correspond to the three lateral edges of a three-sided pyramid. Commonly
the three spines are of equal size, and also the angles between them equal,
so that the pyramid is regular, sometimes very flat, at other times more
elevated. Spicula of exactly the same form are also found in some
#Beloidea#. Probably the three divergent spines are homologous to the
three basal feet of numerous #Spyroidea# and #Cyrtoidea#. The central
capsule, according to Hertwig, is placed in the apical part of the pyramid,
the axes of both being identical, and the porochora resting in the apex
itself. This fact seems to contradict the above-mentioned affinity; but
since in _Triplecta_ and _Triplagia_ the three spines lie horizontally,
they may have changed this original position in different direction, in
_Plagiacantha_ and _Plectophora_ becoming divergent upwards, whereas in
_Plagoniscus_ and _Plectaniscus_ (as in the #Spyroidea# and #Cyrtoidea#)
directed downwards.
The triradial structure, common to the Triplagida and Triplectida, is
replaced by the quadriradial structure in the Tetraplagida and
Tetraplectida. Probably the latter have been derived from the former by
development of a fourth spine, and then this latter would correspond to the
"apical horn" of the other NASSELLARIA. But possibly also both structures
have originated independently from one another. We may distinguish not less
than four different kinds of the quadriradial structure. In the first case
all four spines are equal, and diverge from a common central point at equal
angles in different directions, corresponding to the four axes of a regular
tetrahedron (_Tetraplagia_ and _Tetraplecta_, Pl. 91, figs. 3, 8).
In the second case all four spines are also equal, but they are not united
in a common central point, but opposite in pairs on the two poles of a
common central rod (_Plagonidium_). Therefore the skeleton possesses here
the same form as in the "geminate-biradiate" spicula of many #Beloidea#
(_e.g._, _Thalassoxanthium bifurcum_ and _Sphærozoum furcatum_). The
development of the short horizontal middle rod, connecting the two
divergent pairs of spines, is here probably effected by the porochora of
the central capsule resting upon it.
Whilst in these two cases of quadriradial structure all four spines are
equal, in two other cases they become differentiated in a very remarkable
manner. One spine is vertically directed upwards, in shape and size
different from the three others, which are directed downwards; the former
corresponding probably to the "apical horn," the latter to the three "basal
feet," which are found in the great majority of the #Spyroidea# {902}and
#Cyrtoidea#. Therefore we encounter here for the first time that
characteristic "cortinar structure" which is complete in _Cortina_ and
_Cortiniscus_ (Pl. 92, figs. 11-13, 21), and which may be regarded as the
strongest argument for a close relationship, or even for a common
monophyletic origin of all NASSELLARIA.
The four spines, which we regard therefore as "cortinar spines," exhibit a
twofold kind of central junction. In the simpler case they are united in a
common central point, on which rests the porochora of the central capsule
(_Plagoniscus_ and _Plectaniscus_, Pl. 91, figs. 4, 9). These forms are
nearer to _Cortina_, and may be derived immediately from _Tetraplagia_ and
_Tetraplecta_ by differentiation of the four equal spines. In the other
case the four cortinar spines are separated in pairs, diverging from the
two poles of a short horizontal common "central rod" (_Plagiocarpa_ and
_Periplecta_, Pl. 91, figs. 5, 10). These forms may be compared with the
spicula of some #Beloidea# and derived from _Plagonidium_; but their basal
central rod may be compared again with the basal part of the sagittal ring
of _Cortina_, and this comparison becomes very important in those forms
like _Plagiocarpa procortina_ (Pl. 91, fig. 5). Here the four spines
approach very nearly to those of _Cortina_; the two ventral spines (or
pectoral feet) on the anterior pole of of the middle rod are equal, but
very different from the two dorsal spines, arising from the posterior pole;
the lower odd spine of the latter corresponds to the "caudal foot," the
upper spine to the "apical horn" of _Cortina_ and of the #Cyrtellaria#. The
vertical plane, determined by these two dorsal spines, is the sagittal
plane, and two opposite curved branches which lie in this plane (an upper
arising from the basal part of the apical spine and a lower arising from
the anterior pole of the middle rod) may be regarded as ventral parts of an
incomplete sagittal ring. This interesting form and some other similar
Tetraplagida may be regarded either as beginning #Stephoidea# (_Cortina_,
with incomplete sagittal ring) or as retrograde #Stephoidea# (_Cortina_,
with partly reduced sagittal ring). In every case they seem to indicate the
near relationship between the #Stephoidea# and #Plectoidea#.
Another argument for this close relationship may be found in the position
of the central capsule in the interesting genus _Plagiocarpa_ (Pl. 91, fig.
5). Its basal part (with the porochora) rests upon the common central rod,
its ventral face upon the ventral prolongation of the latter, its dorsal
face upon the apical horn; its axis lies in the sagittal plane. The three
basal spines (the odd caudal and the paired pectoral feet) diverge from its
basal pole downwards in the same manner as in the Cortina, the Zygospyrida
and the Monocyrtida.
Less important than those quadriradial Tetraplagida and Tetraplectida, are
the sexradial #Plectoidea#, the Hexaplagida and Hexaplectida. These may be
derived immediately from the triradial #Plectoidea# by prolongation of the
three primary original spines (of _Plagiacantha_) over the common central
point. Here also two {903}different kinds of central junction are found. In
the simpler case all six radial spines arise from a common central point
(_Hexaplagia_ and _Hexaplecta_). In the other case the six radial spines
arise from the two poles of a short horizontal common central rod, opposed
in two groups, each of three spines (_Plagonium_ and _Plectanium_, Pl. 91,
figs. 6, 11). In this latter case the single corresponding spines of the
two opposite groups are usually parallel, and exhibit therefore exactly the
same characteristic "germinate-triradiate" form which is found in many
#Beloidea# (_e.g._, in the common _Sphærozoum punctatum_ and the similar
_Lampoxanthium punctatum_).
The fourth and last group of this suborder contains the multiradiate
#Plectoidea#, the Polyplagida and Polyplectida. Here the number of radial
spines, diverging from the common centre, exceeds six, and is commonly
seven to nine, at other times ten to twelve or more (_Polyplagia_ and
_Polyplecta_, Pl. 91, fig. 12). When these two genera are better known from
further accurate observations, they may probably be divided into several
different genera (as already proposed in my Prodromus, 1881), since not
only the number, but also the central junction and the arrangement of the
numerous radial spines in the few observed species seems to be very
different. In some seven-radiate species (_e.g._, _Polyplecta heptacantha_)
four larger spines seem to be true "cortinar spines," the three smaller
secondary productions of the former. In the nine-radiate species the nine
spines seem to be sometimes basal branches of three primary spines, at
other times six secondary intercalated between the three primary (like
_Enneaphormis_, Pl. 57, fig. 9). In those multiradial #Plectoidea#, in
which the number of spines amounts to ten or twelve or more, the laws of
disposition are not yet recognised.
Comparing these different productions of the skeleton in the numerous
#Plectoidea#, we find expressed two remarkable and very different
affinities. On the one hand many #Plectoidea# exhibit exactly the same
peculiar forms, which are only found besides in the #Beloidea# (as many
species of _Triplagia_, _Plagiacantha_, _Tetraplagia_, _Plagonidium_,
_Hexaplagia_, and _Plagonium_). On the other hand many #Plectoidea# bear
the same characteristic composition of the skeleton (or the "cortinar
structure") which is found in the Cortinida among the #Stephoidea#, and in
numerous #Spyroidea# and #Cyrtoidea#, which all agree in the possession of
three divergent basal feet and a vertical apical horn. A most important
argument for the close affinity of all these "cortinar NASSELLARIA" seems
to be given by the fact that the sagittal ring, which in _Cortina_ is
combined with the quadriradial structure, exhibits in the #Cyrtellaria# the
most different stages of development; in one group it is complete, in the
second incomplete, and in the third it has completely disappeared.
The form of the radial spines composing the skeleton is usually three-sided
prismatic, gradually tapering from the thicker central base towards the
distal apex; sometimes they are slender pyramidal. More rarely the spines
are cylindrical or slender conical. In the majority of species the spines
are straight, in the minority more or {904}less curved. In very few species
only are they quite simple, without branches. They are nearly always more
or less branched, in many larger species very richly ramified. The modes of
ramification are rather variable. In the majority of #Plectoidea# the
spines are rather regularly verticillate, bearing an increasing number of
verticils, each of which is composed of three divergent branches. These
arise from the three edges of the spine, and all the branches of one edge
are usually parallel, either perpendicular to the spine, or directed at an
acute angle towards its apex. When the verticils are numerous (five to ten
or more), their size commonly tapers gradually towards the apex. Pinnate
spines occur more rarely than verticillate ones; in this case the two
paired lateral edges only of the prismatic spine bear opposite or alternate
branches, whilst the odd middle edge bears no ramules. In some species the
spines are singly or doubly forked. In many species (mainly those with
cylindrical spines) the ramification of the spines is more or less
irregular.
Whilst in all Plagonida the branches of the spine remain perfectly free, in
all Plectanida, again, the meeting ends of the branches become united and
grow together, and by this concrescence a loose network arises, like
wickerwork, which partly encloses the central capsule and the central parts
of the spines, on which it rests. The meshes of this loose wickerwork are
large, either quite irregular, of very different size and form, or more or
less regular, with a certain form and arrangement of the meshes, effected
by the peculiar kind of ramification. Commonly the siliceous threads of the
arachnoidal wickerwork are very thin, often extremely delicate,
representing "pseudopodia metamorphosed into silex." Sometimes the
wickerwork is spongy. Its surface is constantly rough and bristly, with
free ends of the spine-branches, never covered with a regular
lattice-plate, as in the #Cyrtellaria# (#Spyroidea#, #Botryodea#, and
#Cyrtoidea#).
The entire form of the central wickerwork is in the minority of Plectanida
quite irregular and indefinite; in the majority, however, a certain more or
less regular entire form is recognisable, effected by a certain, more or
less regular origin and mode of the connection of the meeting branches. So
in some species of _Triplecta_ (Pl. 91, fig. 7) the network represents a
triangular plate, of _Plectophora_ and _Plectaniscus_ a three-sided
pyramid, of _Tetraplecta_ (Pl. 91, fig. 3) a tetrahedron, and in many other
species a polyhedron of more or less regular form. Some species of
Plectanida become very similar to certain species of #Stephoidea#,
#Spyroidea#, and #Cyrtoidea#; so _Plectaniscus_ and _Periplecta_ approach
to _Cortina_ and _Cortiniscus_, _Pteroscenium_ and _Clathrocorys_, &c.
(compare Pls. 92, 93, 53, 64, &c.). They may represent a true phylogenetic
connection between both groups. But in these cases also the distinction is
determined by the fact that the true #Plectoidea# never possess a complete
sagittal ring (like the #Stephoidea#) nor a regular lattice-shell (like the
#Spyroidea#, #Botryodea#, and #Cyrtoidea#).
{905}_The Central Capsule_ of the #Plectoidea# constantly exhibits the
peculiar characters of the MONOPYLEA or NASSELLARIA. It is commonly ovate,
more rarely ellipsoidal or even spherical, sometimes conical or
lentelliptical. The lower or basal pole of its vertical main axis
constantly exhibits the characteristic "porochora" (or the area porosa) of
the MONOPYLEA, and upon this rests the peculiar "podoconus" (or the
pseudopodial-cone) of this legion. On this porochora the central capsule is
in immediate connection with the central point of the skeleton, or the
horizontal common central rod, from which the radial spines arise. The
endoplasm, or the protoplasm of the central capsule (besides the
podoconus), contains commonly one large alveole or several small vacuoles,
and often pigment-granules. The nucleus is large, spherical or ovate, and
exhibits the same character as in all the other MONOPYLEA; it encloses
usually a single nucleolus.
The position of the central capsule and its topographical relation to the
skeleton offers in the different #Plectoidea# some important and as yet
unsolved problems, which can be answered only by fresh and accurate
observations on living specimens. In _Triplagia_ and _Triplecta_, where the
triangular skeleton lies in a horizontal plane, the vertical main axis of
the central capsule is perpendicular to the central point of that
supporting triangle. In _Plagiacantha_ and _Plectophora_, where the three
radial spines correspond to the edges of a flat pyramid, the capsule is
enclosed in the pyramidal space of the latter, its basal pole touching the
apex; therefore in the normal position of the body the three divergent rays
are directed upwards. In _Tetraplagia_ and _Tetraplecta_ probably the same
position is retained, and therefore the fourth free spine, here developed,
is probably directed vertically downwards. In _Plagoniscus_ and
_Plectaniscus_, however, and moreover, in the closely allied _Plagiocarpa_
and the corresponding _Periplecta_ (Pl. 91, figs. 5, 10) the position of
the central capsule, relative to the skeleton, seems to be inverse, and to
agree with that of the #Stephoidea# (_Cortina_, _Cortiniscus_, &c.) and the
#Cyrtoidea# (_Pteroscenium_, _Clathrocorys_, &c.); the three divergent
spines are here directed downwards (as basal feet), whilst the opposite
fourth spine is vertically directed upwards (as an apical horn); the
capsule rests here upon the tripod, which lies below it, and is inclined
with its dorsal face to the apical spine. In the majority of the other
#Plectoidea# the position of the central capsule and its relation to the
skeleton are not yet sufficiently observed, and require further accurate
researches. Its position seems to be very different in the several genera.
The capsule is never perforated by parts of the skeleton; this latter is
constantly extra-capsular.
The physiological value of the skeleton, with regard to the central
capsule, is different in the Plagonida and Plectanida; in the former it
supports, in the latter it encloses the capsule like a shell. In the
Nassellida, where no skeleton is developed, the central capsule is quite
free and naked, enveloped only by the calymma.
{906}The calymma or the extracapsular jelly-veil in all #Plectoidea# is
voluminous, and encloses not only the central capsule completely, but also
the skeleton wholly or partially. Its form is of the greatest value for the
development and configuration of the skeleton. Sometimes the calymma is
alveolate and foamy, as in _Nassella_ and the common _Thalassicolla_. In
several other #Plectoidea# the calymma seems to include numerous small
vacuoles, sometimes also pigment-granules. Xanthellæ are commonly scattered
in it in great numbers. The pseudopodia, arising in a large bunch from the
porochora of the capsule, and running along the branches of the radial
spines, seem to be always numerous, richly branched, and with a strong
tendency to form anastomoses. The peculiar form of their network is often
exactly preserved in the conformation of the skeleton, produced by them.
The peculiarities of this network require further accurate observations, as
does the whole organisation of the #Plectoidea#.
_Synopsis of the Families of_ #Plectoidea#.
I. Skeleton (originally tripodal) composed of radial
spines united in a common centre and supporting the
central capsule, without wicker-work, 1. PLAGONIDA.
II. Skeleton (originally tripodal) wattled, with irregular
wicker-work, composed of the united branches of radial
spines and enveloping the central capsule, 2. PLECTANIDA.
Family XLVI. #PLAGONIDA#, Haeckel.
_Plagonida_, Haeckel, 1881, Prodromus, p. 423.
_Plagiacanthida_ (_sensu strictiori_), Richard Hertwig, 1879, Organismus
d. Radiol., p. 72.
_Definition._--#Plectoidea# with a spiny skeleton, composed of radial
spines, which arise from a common central point or central rod, and support
the free central capsule.
The family #Plagonida# comprises those NASSELLARIA in which the skeleton is
only composed of united radial spines, arising from a common centre,
without any connection of meeting branches of the spines; the rudimentary
skeleton exhibits therefore neither a loose wickerwork (as in the closely
allied Plectanida), nor a ring (as in the #Stephoidea#), nor a complete
lattice-shell (as in the #Cyrtellaria#, the #Spyroidea#, #Botryodea#, and
#Cyrtoidea#). The central capsule, which possesses all the characters of
the MONOPYLEA, is therefore free, not enclosed, and only on one side
supported or partly protected by the radial spines or their branches.
Two species only of Plagonida have been hitherto known. The first form
described is the _Plagiacantha arachnoides_, discovered thirty years ago
(1855) by Claparède on the western shore of Norway. Another species of the
same genus, from the Mediterranean, was very accurately described by
Richard Hertwig in 1879 in his Organismus der {907}Radiolarien
(_Plagiacantha abietina_). Upon these two species the latter founded his
family Plagiacanthida, a term which was afterwards employed by Bütschli and
others, for the whole group of #Plectoidea#. Many new forms are contained
in the collection of the Challenger, so that we may describe here nine
genera and thirty-four species.
The family Plagonida may be divided into four different subfamilies,
according to the numbers of the radial spines which compose the skeleton:
Triplagida with three, Tetraplagida with four, Hexaplagida with six, and
Polyplagida with numerous (seven to nine or more) radial spines. These are
united commonly in one common central point, upon which rests the basal
pole of the central capsule, with the porochora. More rarely (in the genera
_Plagonidium_, _Plagiocarpa_, and _Plagonium_) the spines arise in two
opposite groups (each with two or three spines) from the two poles of a
common central rod; in this case the basal pole of the central capsule with
the porochora rests upon the horizontal common rod, which corresponds
probably to the basal part of the sagittal ring of the #Stephoidea# and
#Cyrtellaria#.
The different forms which the skeleton of the Plagonida assumes in the
different genera of this family, and the important relations which these
exhibit on the one hand to the spicula of the #Beloidea#, and on the other
hand to the shell of some #Stephoidea# (_Cortina_, _Cortiniscus_, &c.) and
#Cyrtoidea# (_Pteroscenium_, _Clathrocorys_, &c.), have been already
pointed out in the preceding description of the suborder #Plectoidea#.
There it is also demonstrated, that all these different forms may be
derived from the simplest triradial forms, _Triplagia_ and _Plagiacantha_
(compare above, pp. 900-904).
Whilst the genera of the Plagonida are characterised by the number of the
radial spines and the peculiar mode of junction in a common central point
or at the two poles of a common central rod, the different species of this
family may be defined by the peculiar form of the spines and their
branches. These morphological characters have also been already described
above. We repeat here only that the radial spines in the majority of
species are three-sided prismatic and verticillate, each verticil commonly
with three branches. The distal ends of these branches remain constantly
free, and are never united, as is always the case in the following family.
_The Central Capsule_ of the Plagonida exhibits the general characters of
all MONOPYLEA (compare above, p. 890). It is commonly ovate or ellipsoidal,
with vertical main axis; on the lower pole of the latter is the porochora
(or the "area porosa," from which all pseudopodia radiate). This is in
immediate connection with the central point or central rod of the skeleton,
in which its radial spines are united. The topographical relation of the
supporting skeleton to the central capsule seems to exhibit in the
different genera of the Plagonida remarkable differences, as already
demonstrated above (p. 905).
{908}_Synopsis of the Genera of Plagonida._
-------------------------------------------------------------------------
I. Subfamily Triplagida. Three radial spines.
-------------------------------------------------------------------------
Three spines lying in one horizontal plane, 384. _Triplagia_.
Three spines corresponding to the edges of a flat
pyramid, 385. _Plagiacantha_.
-------------------------------------------------------------------------
II. Subfamily Tetraplagida. Four radial spines.
-------------------------------------------------------------------------
{All four spines equal, 386. _Tetraplagia_.
Four spines arising from {
one common central point. {One apical spine
{ opposed to three
{ basal spines, 387. _Plagoniscus_.
{All four spines equal, 388. _Plagonidium_.
Four spines arising in two {
pairs from the poles of a {One apical spine
common central rod. { opposed to three
{ basal spines, 389. _Plagiocarpa_.
-----------------------------------------------------------------
III. Subfamily Hexaplagida. Six radial spines.
-----------------------------------------------------------------
Six spines arising from one common central point, 390. _Hexaplagia_.
Six spines arising in two opposite groups from the
poles of a common central rod, 391. _Plagonium_.
-----------------------------------------------------------------
IV. Subfamily Polyplagida. Numerous radial spines.
-----------------------------------------------------------------
Numerous (seven to nine or more) radial spines
arising from a common centre (either a central
point or a branched rod), 392. _Polyplagia_.
Subfamily 1. TRIPLAGIDA, Haeckel, 1881, Prodromus, p. 423.
_Definition._--#Plagonida# with three radial spines.
Genus 384. _Triplagia_,[3] Haeckel, 1881, Prodromus, p. 423.
_Definition._--#Plagonida# with three radial spines, arising from one
common central point and lying in one horizontal plane.
The genus _Triplagia_ and the following closely allied _Plagiacantha_ may
be regarded as the simplest and most primitive forms of the #Plectoidea#,
perhaps as the common ancestral stock of this suborder. The skeleton is
composed of three simple or branched radial spines, arising from one common
central point. These three spines in _Triplagia_ lie in one and the same
plane, whilst in _Plagiacantha_ they lie in different planes. Therefore the
former exhibits the simplest type of the triradial structure, common to the
majority of NASSELLARIA.
{909}1. _Triplagia primordialis,_ n. sp. (Pl. 91, fig. 2).
Spines straight, of equal size and similar form, equidistant, three-sided
prismatic, each with two pairs of opposite lateral branches, which are
correspondingly parallel to the two other spines; the proximal branches
twice as long as the distal branches.
_Dimensions._--Length of each spine 0.2, of the basal branches 0.07.
_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.
2. _Triplagia triradialis,_ n. sp.
Spines straight, of equal size and similar form, equidistant, three-sided
prismatic, regularly pinnate, with six pairs of opposite pinnulæ, tapering
gradually towards the distal ends; the basal pinnulæ are again branched,
with straight ramules.
_Dimensions._--Length of each spine 0.27, of the basal branches 0.08.
_Habitat._--North Pacific, Station 256, surface.
3. _Triplagia horizontalis,_ n. sp.
Spines curved, cylindrical, irregularly branched, with three primary and
nine to twelve secondary branches, which are also slightly curved. The
angles between the bases of the three spines are equal, but the size and
form of the branches different.
_Dimensions._--Length of the three spines 0.15 to 0.25, of the basal
branches 0.05 to 0.08.
_Habitat._--West Tropical Pacific, Station 226, depth 4475 fathoms.
Genus 385. _Plagiacantha_,[4] Claparède, 1856, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, November 13.
_Definition._--#Plagonida# with three radial spines, arising from one
common central point and corresponding to the edges of a three-sided
pyramid.
The genus _Plagiacantha_ agrees with the preceding _Triplagia_ in the
simple structure of the triradial skeleton, composed of three diverging
radial spines, which are united in a common centre at the oral pole of the
central capsule. But whilst the three radial rods of _Triplagia_ lie in one
horizontal plane, here they lie in different planes and correspond to the
three edges of a flat pyramid. _Plagiacantha arachnoides_, described in
1856 by Claparède, was the earliest known form of all #Plectoidea#.
{910}1. _Plagiacantha arachnoides_, Claparède.
_Plagiacantha arachnoides_, Claparède, 1856, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, November 13.
_Plagiacantha arachnoides_, Claparède, 1858, Études sur les Infusoires et
les Rhizopodes, p. 462 (pl. xxii. fig. 8).
_Acanthometra arachnoides_, Claparède, 1855, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 675.
Spines straight, cylindrical, divided into three divergent straight
branches of equal size; each branch two to three times as long as the
simple thicker basal part.
_Dimensions._--Length of the spines 0.12 to 0.2 of the branches 0.08 to
0.14.
_Habitat._--North Atlantic, coast of Norway, Claparède, surface.
2. _Plagiacantha furcata_, n. sp.
Spines straight, cylindrical, divided into two divergent straight branches
of equal size, of about the same length as the simple basal part. The
spines and their branches are smooth.
_Dimensions._--Length of the spines 0.24, of their fork-branches 0.12.
_Habitat._--North Pacific, Station 254, surface.
3. _Plagiacantha dodecantha_, n. sp.
Spines straight, three-sided prismatic, in the middle with one verticil
composed of three divergent straight branches of equal size, of about the
same length as the simple basal part. The edges of the spines and their
branches are thorny.
_Dimensions._--Length of the spines 0.24, of the branches 0.1.
_Habitat._--Central Pacific, Station 274, surface.
4. _Plagiacantha abietina_, Richard Hertwig.
_Plagiacantha abietina_, Richard Hertwig, 1879, Organismus d. Radiol., p.
72, Taf. vii. figs. 6-6_b_.
Spines straight, three-sided prismatic, with three verticils of three
divergent straight lateral branches, decreasing in size towards the distal
end; the branches of the first verticil about twice as long as those of the
second, and four times as long as those of the third verticil. All nine
branches of each spine simple, straight, three-sided pyramidal.
_Dimensions._--Length of the spines 0.2 to 0.3, of the basal branches 0.06
to 0.08.
_Habitat._--Mediterranean, Messina (R. Hertwig), surface.
5. _Plagiacantha verticillata_, n. sp.
Spines curved, three-sided prismatic, with six to nine verticils of three
divergent branches, decreasing in size towards the distal end; the branches
of the first verticil about twice as long as those of the fourth verticil.
All branches simple, slightly curved, bristle-shaped.
_Dimensions._--Length of the spines 0.27, of the basal branches 0.12.
_Habitat._--South Pacific, Station 296, surface.
{911}6. _Plagiacantha elatine_, n. sp.
Spines straight, three-sided prismatic, with prominent wing-like edges and
ten to twelve verticils of three divergent branches, decreasing in size
towards the distal end; the branches of the three or four basal verticils
are again ramified and much larger than the simple branches of the distal
verticils.
_Dimensions._--Length of the spines 0.36, of the basal branches 0.14.
_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.
Subfamily 2. TETRAPLAGIDA, Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plagonida# with four radial spines.
Genus 386. _Tetraplagia_,[5] Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plagonida# with four equal radial spines, arising from one
common central point, and corresponding to the four axes of a tetrahedron.
The genus _Tetraplagia_ is one of the most important #Plectoidea#, and
possibly the common ancestral form of many NASSELLARIA (compare above, p.
901). The skeleton is composed of four radial rods, diverging from one
common centre in different directions, and corresponding to the four axes,
which extend from the central point of a tetrahedron to the central points
of its four faces. The whole skeleton of _Tetraplagia_ exhibits therefore
the same form, which is observed in the single quadriradiate spicula of
some #Beloidea# (in some species of _Lampoxanthium_, _Sphærozoum_, &c.).
1. _Tetraplagia geometrica_, n. sp.
Spines straight, cylindrical, perfectly equal, corresponding in regular
disposition exactly to the four geometrical axes of a regular tetrahedron;
in the middle arise from each spine two opposite equal lateral branches of
half the length of the spine.
_Dimensions._--Length of the spines 0.12, of the branches 0.06.
_Habitat._--Central Pacific, Station 266, surface.
2. _Tetraplagia phænaxonia_, n. sp. (Pl. 91, fig. 3).
Spines straight or slightly curved, three-sided prismatic, with irregular
short branches arising from the three edges; the branches are thorny,
tapering towards the apex.
_Dimensions._--Length of the spines 0.15, of the basal branches 0.03.
_Habitat._--Tropical Atlantic, Station 332, surface.
{912}3. _Tetraplagia abietina_, Haeckel.
_Plagiacantha abietina_, var. _quadrispina_, Richard Hertwig, 1879,
Organismus d. Radiol., p. 73.
Spines straight, three-sided prismatic, verticillate, with six to eight
verticils of three simple straight branches; the branches of each edge are
parallel, tapering towards the distal end. R. Hertwig regards this species
only as a four-spined variety of his three-spined _Plagiacantha abietina_;
but a specimen, observed by me in Corfu, exhibited all the characters of
_Tetraplagia_.
_Dimensions._--Length of the spines 0.2, of the basal branches 0.07.
_Habitat._--Mediterranean (Messina, Corfu), surface.
Genus 387. _Plagoniscus_,[6] n. gen.
_Definition._--#Plagonida# with four unequal radial spines, arising from
one common central point; one vertical or apical spine opposed to three
divergent or basal spines.
The genus _Plagoniscus_ agrees with the preceding _Tetraplagia_ (its
probable ancestral form) in the possession of four radial spines, diverging
from one common central point. But whilst in this latter all four spines
are equal, corresponding exactly to the four axes of a tetrahedron, here in
_Plagiocarpa_ an important difference exists between one vertical or apical
spine and three other divergent basal spines; these latter corresponding
probably to the three "feet," the former to the single "apical horn" of the
majority of NASSELLARIA. Perhaps we find here one of the oldest and
simplest types of their "triradial or cortinar structure" (compare above,
p. 902).
1. _Plagoniscus tripodiscus_, n. sp. (Pl. 91, fig. 4).
Spines three-sided prismatic, thorny. Apical spine nearly straight,
verticillate, with four to five verticils of three thorny branches,
tapering towards the apex. Three basal spines somewhat shorter, curved,
with three thorny edges.
_Dimensions._--Length of the apical spine 0.2, of the basal spines 0.15.
_Habitat._--Central Pacific, Station 263, surface.
2. _Plagoniscus euscenium_, n. sp.
Spines three-sided prismatic, thorny, with dentate edges, and three to six
verticils of three short branches. Apical spine straight, with six
verticils, nearly twice as long as the three curved basal spines, each of
which bears three verticils; the basal verticils larger and ramified.
Resembles somewhat Euscenium eucolpium, Pl. 53, fig. 12, but has no
latticed shell.
_Dimensions._--Length of the apical spine 0.3, of the basal spines 0.16.
_Habitat._--North Pacific, Station 247, surface,
{913}3. _Plagoniscus cortinaris_, n. sp.
Spines three-sided prismatic, straight, verticillate. Apical spine with
twelve verticils, one and a half times as long as the three basal spines,
each of which bears eight verticils of three branches. The branches are
also prismatic, straight, on each edge parallel, tapering towards the apex,
in the three basal spines forked, in the apical spine more branched.
Similar to the cortinar skeleton of _Clathrocorys_ (Pl. 64, figs. 8-10).
_Dimensions._--Length of the apical spine 0.24, of the basal spines 0.16.
_Habitat._--South Atlantic, Station 338, surface.
4. _Plagoniscus nassellaris_, n. sp.
Spines cylindrical, curved, irregularly branched. Apical spine half as long
as, and less branched than the three basal spines, which are sigmoidal,
nearly horizontally expanded in the proximal half, descending in the distal
half.
_Dimensions._--Length of the apical spine 0.1, of the three basal spines
0.18.
_Habitat._--West Tropical Pacific, Station 224, surface.
Genus 388. _Plagonidium_,[7] Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plagonida# with four equal radial spines, arising in pairs
from the two poles of a common central rod.
The genus _Plagonidium_, and the following _Plagiocarpa_ possess four
radial spines, like the two preceding genera. But whilst the four rods in
these latter arise from a common centre, here they arise in two pairs from
the two poles of a common middle rod; they have therefore exactly the same
form which we find in the single spicula of some #Beloidea# (e.g.,
_Thalassoxanthium furcatum_, _Sphærozoum furcatum_, &c.). Probably the
middle rod is horizontal and serves as supporting base for the central
capsule, whilst two opposite spines are directed upwards, two other
downwards.
1. _Plagonidium bigeminum_, n. sp.
Spines straight, three-sided prismatic, four to six times as long as the
common central rod, pinnate, with four to five pairs of opposite pinnulæ,
the distal of which are simple, the proximal again branched.
_Dimensions._--Length of the spines 0.16, of the middle rod 0.032.
_Habitat._--Indian Ocean, Sunda Strait (Rabbe), surface.
{914}2. _Plagonidium quadrigeminum_, n. sp.
Spines cylindrical, curved, eight to ten times as long as the common
central rod, in the distal half forked; the fork-branches curved, somewhat
longer than the basal part.
_Dimensions._--Length of the spines 0.18, of the middle rod 0.02.
_Habitat._--Antarctic Ocean, Kerguelen Island, Station 159, surface.
Genus 389. _Plagiocarpa_,[8] Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plagonida# with four unequal radial spines, arising in
pairs from the two poles of a common central rod; one ascending apical
spine opposed to three descending basal spines.
The genus _Plagiocarpa_ agrees with the preceding _Plagonidium_ in the
possession of a common horizontal middle rod, the two poles of which bear
two pairs of divergent spines; but whilst in the preceding all four spines
are equal, here they are differentiated in the same manner as in
_Plagoniscus_, which differs only in the absence of the middle rod. The two
observed and closely allied species of this genus are of peculiar interest,
since they belong possibly to the common ancestral forms of the
NASSELLARIA; the basal middle rod corresponds perhaps to the basal part of
a sagittal ring, the apical spine to its dorsal part, the three other
spines to the basal feet (compare above, p. 902).
1. _Plagiocarpa procortina_, n. sp. (Pl. 91, fig. 5).
Spines cylindrical, curved, thorny, three to four times as long as the
common middle rod. Apical spine and the meeting caudal spine (or the
posterior basal spine) somewhat longer and with more numerous thorns than
the two paired pectoral (or anterior) spines. From the common base of the
latter arises an anterior prolongation of the horizontal middle rod, which
in the sagittal plane is curved upwards and corresponds to the sternal foot
of many #Cyrtellaria#. An ascending branch of this spine is opposed to a
descending branch of the apical spine, both together forming an incomplete
sagittal ring.
_Dimensions._--Length of the two larger spines 0.15, of the two smaller
0.12.
_Habitat._--Mediterranean (Portofino near Genoa), surface.
2. _Plagiocarpa procyrtella_, n. sp.
Spines of form and arrangement similar to those of the preceding species,
but longer and more branched, six to eight times as long as the shorter
common middle rod. The two characteristic {915}opposed branches (the
ascending branch of the basal rod and the descending branch of the apical
spine), which in the preceding species nearly compose a sagittal ring, are
here absent.
_Dimensions._--Length of the two larger 0.27, of the two smaller 0.21.
_Habitat._--North Atlantic, Iceland (Steenstrup), surface.
Subfamily 3. HEXAPLAGIDA, Haeckel.
_Definition._--#Plagonida# with six radial spines.
Genus 390. _Hexaplagia_,[9] Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plagonida# with six radial spines, arising from one common
central point.
The genus _Hexaplagia_ differs from the preceding genera of Plagonida in
the possession of six radial spines, diverging from one common central
point. Commonly, these six spines seem to lie opposite in pairs in three
different meridian planes, and in this case _Hexaplagia_ may be regarded as
a _Plagiacantha_, the three radial spines of which are prolonged over the
basal pole of the central capsule. But in other species the six spines seem
to lie in different planes. Further observations are required.
1. _Hexaplagia arctica_, n. sp.
Spines opposite in pairs in three diameters, crossed in the common centre,
straight, three-sided prismatic, with dentate edges. The three pairs are
equal, but the upper spine of each pair only half as long as the lower
spine.
_Dimensions._--Length of the upper spine 0.13, of the lower 0.27.
_Habitat._--Arctic Ocean (Greenland), in the stomach of a Medusa (Olrik).
2. _Hexaplagia antarctica_, n. sp.
Spines opposite in pairs in three diameters, crossed in the common centre,
slightly curved, three-sided prismatic, with verticillate branches; the
three pairs are equal, but the lower spine of each pair bears three to four
verticils, each of three branches, and is two to three times as long as the
upper spine, which bears two verticils only.
_Dimensions._--Length of the upper spine 0.12, of the lower 0.3.
_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms.
{916}3. _Hexaplagia collaris_, n. sp.
Spines in opposite pairs in three diameters, crossed in the common centre,
straight, cylindrical, pinnate, with three to four pairs of opposite
lateral branches or regular pinnulæ. All six spines are equidistant, of
equal size and similar form, and lie with their branches nearly in one
horizontal plane. Therefore they are similar to the six radial rods in the
collar septum of many #Spyroidea# and #Cyrtoidea# (_e.g._, _Calpophæna_,
Pl. 53, fig. 18).
_Dimensions._--Length of all six spines 0.18, of their basal pinnulæ 0.04.
_Habitat._--East of New Zealand, Station 169, surface.
4. _Hexaplagia australis_, n. sp.
Spines unequal, at unequal intervals, not opposite in pairs, cylindrical,
irregularly branched and curved. In this species a definite arrangement of
the six different spines could not be detected.
_Dimensions._--Length of the spines 0.2 to 0.3, of their largest branches
0.1.
_Habitat._--South of Australia, Station 160, surface.
Genus 391. _Plagonium_,[10] Haeckel, 1881, Prodromus, p. 423.
_Definition._--#Plagonida# with six radial spines, arising in two opposite
divergent groups from the two poles of a common central rod.
The genus _Plagonium_ differs from the preceding closely allied
_Hexaplagia_ in the remarkable peculiarity, that the six radial spines do
not arise from one common central point, but from the two poles of a common
horizontal middle rod; three divergent spines on each pole. The skeleton of
_Plagonium_ exhibits therefore the same remarkable form which is found in
the isolated spicula of numerous #Beloidea# (_e.g._, _Lampoxanthium
punctatum_, _Sphærozoum punctatum_), and bears the same relation to
_Hexaplagia_ that _Plagonidium_ does to _Tetraplagia_.
1. _Plagonium sphærozoum_, n. sp. (Pl. 91, fig. 6).
Spines straight and stout, three-sided prismatic, about twice as long as
the common middle rod, irregularly branched or nearly verticillate, with
short thorny branches. Similar to the single spicula of some species of
_Sphærozoum_ and _Lampoxanthium_.
_Dimensions._--Length of the spines 0.12, of the middle rod 0.06.
_Habitat._--Equatorial Atlantic, Station 347, surface.
{917}2. _Plagonium lampoxanthium_, n. sp.
Spines irregularly curved, slender, cylindrical, six to eight times as long
as the common middle rod, in the proximal half smooth, in the distal half
covered with short thorns. (Similar to an isolated spiculum of
_Lampoxanthium punctatum_ or of _Sphærozoum variabile_, Pl. 4, fig. 5.)
_Dimensions._--Length of the spines 0.18, of the middle rod 0.03.
_Habitat._--North Pacific, Station 240, surface.
3. _Plagonium arborescens_, n. sp.
Spines irregularly curved and branched, slender, cylindrical, thorny,
twelve to sixteen times as long as the middle rod; the branches are large,
arborescent, their ramules again ramified and very thorny.
_Dimensions._--Length of the spines 0.2 to 0.25, of the middle rod 0.02.
_Habitat._--Indian Ocean, Madagascar (Rabbe), surface.
4. _Plagonium trigeminum_, n. sp.
Spines straight, slender, cylindrical, four to six times as long as the
middle rod, in the basal half smooth, in the distal half arborescent, with
three to four irregular verticils of ramified branches. (Similar to a
single spiculum of _Sphærozoum verticillatum_, Pl. 4, fig. 7.)
_Dimensions._--Length of the spines 0.15 to 0.2, of the middle rod 0.05.
_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.
5. _Plagonium distriactis_, n. sp.
Spines straight and stout, three-sided prismatic, smooth, ten to twelve
times as long as the middle rod; each on the distal end cleft into three
divergent straight branches, which are again trichotomous.
_Dimensions._--Length of the spines 0.15 to 0.18, of the middle rod 0.015.
_Habitat._--South Pacific, Station 288, surface.
Subfamily 4. POLYPLAGIDA, Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plagonida# with numerous (seven to nine or more) radial
spines.
Genus 392. _Polyplagia_,[11] n. gen.
_Definition._--#Plagonida# with numerous (seven to nine or more) radial
spines, arising from a common centre and lying in different planes.
{918}The genus _Polyplagia_ alone represents the small subfamily of
Polyplagida, distinguished from the other Plagonida by the multiplication
of the radial spines, the number of which amounts to seven to nine or more.
This increased number is commonly the result of an intercalation of new
spines between the three or four primary spines; it is sometimes also
effected by stronger development of branches of the latter, which become
independent. The following five species of this genus are very different,
require further investigation, and perhaps represent different genera:--
1. _Polyplagia septenaria_, n. sp.
Seven radial spines, straight, three-sided prismatic, verticillate, of
different sizes; four larger spines correspond to the four axes of a
tetrahedron (running from the centre to the four corners), each with five
to six verticils of three simple slender branches; one of these four main
spines seems to be the apical, the three others the basal spines of
_Plagiocarpa_; in the three meridian planes between the latter and the
former lie the three smaller spines, diverging upwards, each with two to
three verticils. (Similar to _Polyplecta heptacantha_, Pl. 91, fig. 12, but
without connection between the branches.)
_Dimensions._--Length of the four major spines 0.26, of the three minor
0.11.
_Habitat._--Central Pacific, Station 274, surface.
2. _Polyplagia octonaria_, n. sp.
Eight radial spines, straight, three-sided prismatic, of equal size,
arising in two opposite groups from the two poles of a short common middle
rod (as in _Sphærozoum arborescens_, Pl. 4, fig. 8, and in other
#Beloidea#). The four spines of each group are divergent, six to eight
times as long as the middle rod, each spine armed with three to four
verticils of thorny branches.
_Dimensions._--Length of the spines 0.15, of the middle rod 0.022.
_Habitat._--Indian Ocean, Cocos Islands (Rabbe), surface.
3. _Polyplagia novenaria_, n. sp.
Nine radial spines of equal size, straight, cylindrical, lying nearly in a
horizontal plane, or forming a very flat pyramid. Near the common central
point every three spines arise from a short common rod, so that the centre
of the skeleton is triradial. Each spine bears towards the apex two
divergent straight lateral branches. This species may have been derived
from _Plagiacantha arachnoides_ by shortening and reduction of the basal
parts of the three original branched primary spines.
_Dimensions._--Length of the nine spines 0.24, of the three basal rods
0.02.
_Habitat._--North Atlantic, Færöe Channel (Gulf Stream), John Murray,
surface.
4. _Polyplagia duodenaria_, n. sp.
Twelve radial spines of equal size, arising from a common central point,
and diverging in different directions. The twelve spines are very large,
opposite in six pairs, cylindrical, longitudinally {919}striped (the
expression of concentric lamellæ), and with spinulate surface, covered with
innumerable small thorns. The basal quarter of each spine is straight and
simple, the second quarter twice forked, and these four fork-branches are
again in the outer half of the spine richly forked or ramified, with
diverging, slightly curved thin branches; each of the twelve spines with
about sixty to eighty terminal branches, the ends of which seem to fall
into a spherical face. The position of this remarkable species in this
family is doubtful.
_Dimensions._--Length of the spines 0.12 to 0.16, of the simple basal part
0.04.
_Habitat._--South Pacific (off Juan Fernandez), Station 299, surface.
5. _Polyplagia viminaria_, n. sp.
Numerous (sixteen to twenty or more) radial spines of about equal size,
arising from a common central point and diverging in different directions,
richly and more or less irregularly branched. The ends of the numerous
small branches seem to fall into a spherical face. The large spines of this
species have the same form and structure as in the preceding, nearly allied
species, but are more numerous and more irregularly branched and disposed.
_Dimensions._--Length of the spines 0.2 to 0.25, of the simple basal part
0.05.
_Habitat._--North Pacific, Station 241, surface.
Family XLVII. #Plectanida#, Haeckel.
_Plectanida_, Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plectoidea# with a wattled skeleton, composed of the
meeting and united branches of radial spines, which arise from a common
central point or central rod, and protect the partly enclosed central
capsule.
The family #Plectanida# comprises those NASSELLARIA in which the skeleton
is composed of radial spines, arising from a common centre, and of a loose
wickerwork, produced by concrescence of the meeting branches of those
spines. This rudimentary wattled skeleton is either quite irregular or only
slightly regular, but it never assumes the form of a complete
lattice-shell, as in the #Cyrtellaria# (the #Spyroidea#, #Botryodea#, and
#Cyrtoidea#), nor does it exhibit a ring (as in the #Stephoidea#). The
central capsule is partly or wholly protected, and often entirely enclosed
by the wattled skeleton.
Three species only of Plectanida have been hitherto known. The first
described form is _Plectophora arachnoides_, which its discoverer Claparède
observed in a living state in 1855 on the western coast of Norway, and
considered as a mere variety of his _Plagiacantha arachnoides_. Two other
species were afterwards observed in the Mediterranean, _Polyplecta
dumetum_, 1856, by Johannes Müller (united by him with _Acanthodesmia_) and
_Polyplecta polybrocha_ by myself in 1864. Many new forms are found in the
{920}collection of the Challenger, so that we may here distinguish eight
genera and twenty-seven species.
The family Plectanida may be divided into four different subfamilies,
according to the number of the radial spines which compose the skeleton.
Those four subfamilies, as also the genera contained in them, correspond
exactly to the four subfamilies of Plagonida, from which they have
originated: Triplectida with three, Tetraplectida with four, Hexaplectida
with six, and Polyplectida with numerous (seven to nine or more) radial
spines. These spines are usually united (as in the corresponding ancestral
Plagonida) in one common central point, upon which rests the basal pole of
the central capsule, with the porochora. More rarely (in the genera
_Periplecta_ and _Plectanium_) the spines arise in two opposite groups
(each of two or three spines) from the two poles of a common horizontal
central rod, which supports the overlying porochora of the central capsule.
The different genera of Plectanida, which are enumerated in the following
synopsis, correspond so exactly to the different genera of Plagonida
described above, that probably each of the former has arisen from a
corresponding genus of the latter. The only difference between the two is,
that in all Plagonida the branches and ramules of the radial spines end
freely, without growing together, whilst in all Plectanida the meeting ends
of the neighbouring spines grow together and so produce a loose and
irregular wickerwork. Therefore the latter constantly possess meshes, which
are missing in the former. As soon as any form of Plagonida begins to
produce meshes by concrescence of meeting branches of the spines, it passes
over into a corresponding form of Plectanida. The loose wickerwork or
wattlework so produced is sometimes very irregular, at other times more or
less regular; but it never assumes the regular form of a complete
lattice-shell, as in the #Cyrtellaria# (#Spyroidea#, #Botryodea#, and
#Cyrtoidea#). The general differences which this wickerwork exhibits in the
different genera of Plectanida have been already described above (compare
pp. 900-904).
_The Central Capsule_ of the Plectanida agrees perfectly with that of the
ancestral Plagonida, as well in general form and structure as in the
peculiar topographical relation to the radial spines (compare above, p.
905). A slight difference between the two families is effected by the
higher development of the skeleton in the Plectanida. Since the branches of
the radial spines in this family become united and form a loose wickerwork,
the central capsule becomes more or less enclosed by the latter, and more
perfectly protected, than in the Plagonida, where the branches remain free.
In this respect the Plectanida approach more nearly to the #Cyrtoidea# with
which they are connected by such transitional forms as _Plectaniscus_ and
_Periplecta_ on the one hand, _Cladoscenium_ and _Pteroscenium_ on the
other.
{921}_Synopsis of the Genera of Plectanida._
-------------------------------------------------------------------------
I. Subfamily Triplectida. Three radial spines.
-------------------------------------------------------------------------
Three spines lying in one horizontal plane, 393. _Triplecta_.
Three spines corresponding to the edges of a flat
pyramid, 394. _Plectophora_.
-------------------------------------------------------------------------
II. Subfamily Tetraplectida Four radial spines.
-------------------------------------------------------------------------
{ All four spines equal, 395. _Tetraplecta_.
Four spines arising from {
one common central { One apical spine opposed
point. { to three basal spines, 396. _Plectaniscus_.
Four spines arising in two pairs from the poles of
a common central rod; one apical spine different
common spines, 397. _Periplecta_.
-----------------------------------------------------------------
III. Subfamily Hexaplectida. Six radial spines.
-----------------------------------------------------------------
Six spines arising from one common central point, 398. _Hexaplecta_.
Six spines arising in two opposite groups from the
poles of a common control rod, 399. _Plectanium_.
-----------------------------------------------------------------
IV. Subfamily Polyplectida. Numerous radial spines.
-----------------------------------------------------------------
Numerous (seven to nine or more) radial spines
arising from a common centre (either a central
point or a branched rod), 400. _Polyplecta_.
Subfamily 1. TRIPLECTIDA, Haeckel, 1881, Prodromus, p. 424.
_Definition_.--#Plectanida# with three radial spines.
Genus 393. _Triplecta_,[12] Haeckel, 1881, Prodromus, p. 424.
_Definition_.--#Plectanida# with three radial spines, arising from one
common central point and lying in one horizontal plane.
The genus _Triplecta_ is the simplest and most primitive of the Plectanida,
and may therefore be regarded as the prototype of this family. The skeleton
represents a triangular lattice-plate with three radial beams. On the
central union of the latter rests the oral pole of the central capsule.
Since the axis of the latter is vertical, the lattice-plate must be
horizontal, serving for the expansion of the pseudopodia. _Triplecta_ has
arisen from _Triplagia_ by union of the branches of its three radial
spines. In the simplest case only three large meshes are formed,
corresponding probably to the three cortinar meshes in the collar septum of
many #Cyrtellaria#.
1. _Triplecta triangulum_, n. sp.
Spines straight, equal, smooth, cylindrical, each in the basal half with
one pair of divergent straight lateral branches. The opposed branches of
every two neighbouring spines are united by a {922}thin convex bow. In this
way arises a very simple, equilateral triangular skeleton, with three equal
large meshes.
_Dimensions._--Length of the spines 0.14, sides of the triangle 0.16.
_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms.
2. _Triplecta triactis_, n. sp. (Pl. 91, fig. 7).
Spines straight, equal, three-sided prismatic, pinnate, each with three to
four pairs of opposite slender pinnulæ or lateral branches; the pinnulæ of
each spine are correspondingly parallel to the main rods of the other two
spines. All pinnulæ branched and connected by a few slender bows, marking
the sides of a regular triangle.
_Dimensions_.--Length of the spines 0.15, sides of the triangle 0.17.
_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.
Genus 394. _Plectophora_,[13] Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plectanida# with three radial spines, arising from one
common central point and corresponding to the edges of a three-sided
pyramid.
The genus _Plectophora_ has been derived from _Plagiacantha_ by union of
the meeting neighbouring branches of the three radial spines, and exhibits
therefore to it the same relation that _Triplecta_ bears to _Triplagia_.
The loose framework so produced corresponds to the three sides of a flat
pyramid and supports the central capsule.
1. _Plectophora triomma_, n. sp.
Spines equal, straight, three-sided prismatic, thorny, connected by three
convex bows, the meeting branches of lateral spines arising in one pair
from the middle part of each spine. Therefore the skeleton exhibits three
large ovate meshes only.
_Dimensions._--Length of the spines 0.12, of the meshes 0.08.
_Habitat._--North Pacific, Station 238, surface.
2. _Plectophora arachnoides_, Haeckel.
_Plagiacantha arachnoides_, var., Claparède, 1858, Études sur les
Infusoires et les Rhizopodes, p. 462, Taf. xxii. fig. 9.
Spines straight, cylindrical, trifid, with one pair of lateral branches.
The nine diverging, straight, and smooth branches are connected in the
distal part by slender concave bows, so that the whole skeleton exhibits
nine wide meshes, three larger pentagonal and six smaller triangular.
_Dimensions._--Length of the spines 0.14, of their branches 0.07.
_Habitat._--North Atlantic, west coast of Norway (Claparède), surface.
{923}3. _Plectophora novena_, n. sp.
Spines slightly curved, three-sided prismatic, thorny, with two pairs of
lateral branches. The six smaller distal branches end freely, whilst the
six larger basal branches are connected by slender convex bows. There are
therefore nine wide meshes, as in the preceding closely allied species.
_Dimensions._--Length of the spines 0.18, of the basal branches 0.08.
_Habitat._--North Atlantic, Færöe Channel (Gulf Stream) (John Murray),
surface.
4. _Plectophora pyramidalis_, n. sp.
Spines straight, three-sided prismatic, with three to four verticils of
short lateral branches. The branches of the basal verticils are again
ramified, and form by connecting bows a delicate loose framework, covering
the three sides of a flat pyramid, the three edges of which are the three
radial spines.
_Dimensions._--Length of the spines 0.2, base of the pyramid 0.16.
_Habitat._--Central Pacific, Station 267, surface.
Subfamily 2. TETRAPLECTIDA, Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plectanida# with four radial spines.
Genus 395. _Tetraplecta_,[14] Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plectanida# with four equal radial spines, arising from one
common central point and corresponding to the four axes of a tetrahedron.
The genus _Tetraplecta_ has been derived from _Tetraplagia_ by union of the
neighbouring branches of the four radial spines, diverging from a common
point in different directions. In some forms of this genus the four rods
seem to correspond exactly to the four axes, which are directed from the
centre of a tetrahedron towards its four corners; whilst in other forms the
four rods and the angles between them are perhaps not perfectly equal.
1. _Tetraplecta tetrahedra_, n. sp.
Spines straight, equal, three-sided prismatic, pinnate, each with three or
four pairs of opposite straight slender pinnulæ or lateral branches; the
pinnulæ of each side are correspondingly parallel. {924}All pinnulæ
connected by a few slender bridges, thus producing a delicate network with
irregular rhomboidal meshes.
_Dimensions._--Length of the spines 0.15, of the basal branches 0.05.
_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.
2. _Tetraplecta quadricornis_, n. sp.
Spines in the basal half straight, in the distal half slightly curved and
irregularly branched, with two to three pairs of unequal alternate lateral
branches, the distal ends of which are connected by a few slender bows,
marking the six edges of an irregular tetrahedron.
_Dimensions._--Length of the spines 0.22, of the basal branches 0.14.
_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.
3. _Tetraplecta pinigera_, n. sp. (Pl. 91, fig. 8).
Spines three-sided prismatic, straight, or in the basal half slightly
curved, verticillate; each spine with six to eight three-branched regular
verticils, tapering gradually towards the distal end. All branches of each
spine lie parallel in three equidistant meridian planes, and are connected
by delicate parallel threads, perpendicular to the branches. Therefore the
skeleton consists of four pine-shaped trees and twelve delicate triangular
wings with rectangular meshes.
_Dimensions._--Length of the spines 0.25 to 0.3, of the basal branches 0.1
to 0.15.
_Habitat._--Central Pacific, Station 271, surface.
Genus 396. _Plectaniscus_,[15] nov. gen.
_Definition._--#Plectanida# with four unequal radial spines, arising from
one common central point; one vertical or apical spine opposed to three
divergent or basal spines.
The genus _Plectaniscus_ has probably been derived from _Plagoniscus_ by
reticular union of the neighbouring branches of the four radial spines, and
exhibits therefore to it the same relation that _Tetraplecta_ bears to
_Tetraplagia_. Whilst in these two latter genera the four spines are equal,
in the two former genera there is an important difference between a
vertical spine (or apical horn) and three divergent (commonly larger)
spines, corresponding to the three basal feet of the triradiate
NASSELLARIA. Perhaps, therefore, _Plectaniscus_ is one of the remotest
ancestors of the latter; but differs in the absence of a complete
lattice-shell.
{925}1. _Plectaniscus cortiniscus_, n. sp. (Pl. 91, fig. 9).
Spines straight, three-sided prismatic, with three to four verticils of
short perpendicular branches; the branches of the distal verticils are
simple and free, those of the proximal verticils again ramified and
connected by an arachnoidal network of delicate threads. The vertical
apical spine (or horn) is scarcely one-third or half as long as the three
divergent basal spines (or feet), and the angle between it and the latter
is smaller.
_Dimensions._--Length of the apical spine 0.05 to 0.1, of the three basal
spines 0.18 to 0.2.
_Habitat._--North Pacific, Station 244, surface.
2. _Plectaniscus tripodiscus_, n. sp.
Spines curved, cylindrical, with a variable number of irregular branches,
which in the distal half of the spines are free, in the basal half again
ramified and connected by a loose spongy framework. The apical spine is
shorter and simpler, nearly straight, less ramified.
_Dimensions._--Length of the apical spine 0.1, of the three basal spines
0.15 to 0.18.
_Habitat._--North Pacific, Station 238, surface.
3. _Plectaniscus archiscenium_, n. sp.
Spines slightly curved, three-sided prismatic, with two to three verticils
of short curved branches. The vertical apical spine is about twice as long
as the three basal spines, and connected with them by an irregular loose
framework. The three basal spines are connected together only by a simple
ring, so that between them remain three large collar holes, like those of
the similar and closely allied _Archiscenium quadrispinum_ (Pl. 53, fig.
11).
_Dimensions._--Length of the apical spine 0.32, of the three basal spines
0.18.
_Habitat._--South Pacific, Station 295, depth 1500 fathoms.
4. _Plectaniscus cladoscenium_, n. sp.
Spines curved, three-sided prismatic. The three basal spines pinnate, with
four to five pairs of opposite curved pinnulæ; the distal pairs are simple
and free, the basal pairs branched and connected by an irregular delicate
framework, which together with the apical spine forms a spongy cap-shaped
shell, similar to _Cladoscenium_. Apical spine about half as long, simple.
_Dimensions_.--Length of the apical spine 0.1, of the three basal spines
0.18.
_Habitat._--Central Pacific, Station 274, surface.
5. _Plectaniscus clathrocorys_, n. sp.
Spines straight, three-sided prismatic, with seven or eight verticils of
ramified branches, which in the basal half are connected by an irregular
loose framework. In the distal half each of the three divergent basal
spines (or feet) is connected with the longer apical spine (or horn) by a
{926}fenestrated triangular lattice wing. Therefore the skeleton becomes
very similar to _Clathrocorys_ (Pl. 64, figs. 8-10), but wants the regular
central cephalis.
_Dimensions._--Length of the apical spine 0.2, of the basal spines 0.14.
_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.
Genus 397. _Periplecta_,[16] Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plectanida# with four unequal radial spines, arising in
pairs from the two poles of a common central rod; one ascending apical
spine opposed to three descending basal spines.
The genus _Periplecta_ has probably been derived from _Plagiocarpa_ (by
concrescence of the meeting spine branches), and has the same important
relation to a part of the triradial #Stephoidea# (_Cortina_, &c.) and
#Cyrtoidea# (_Pteroscenium_, &c.). It differs from the latter only in the
fact that the loose irregular framework connecting the bases of the four
cortinar spines is not a regular lattice-shell.
1. _Periplecta cortina_, n. sp. (Pl. 91, fig. 10).
Spines of very different size and shape, three-sided prismatic. The apical
spine (or horn) is larger, nearly straight, and bears a verticil of three
large divergent branches, which are again ramified. The three basal spines
(or feet) are curved, pinnate, each with three to five pairs of opposite
simple curved branches. A small common central rod separates the two united
pectoral feet from the two other spines (the caudal foot and the apical
horn). The three basal feet are connected by three convex bows composing a
horizontal collar ring, and since the central rod is prolonged between the
pectoral feet to the ring, a very remarkable collar septum is formed with
four cortinar meshes. Above this septum an irregular spongy shell,
including the central capsule, is formed by a delicate framework,
interwoven between the apical horn and the three basal feet.
_Dimensions._--Length of the apical spine 0.25 to 0.3, of the three basal
spines 0.15 to 0.2.
_Habitat._--Central Pacific, Station 271, surface.
2. _Periplecta pteroscenium_, n. sp.
Spines of very different size and shape, three-sided prismatic,
verticillate. The apical spine (or horn) with ten to twelve verticils, is
one and a half times as long as the three basal spines (or feet), which
bear six to eight verticils only; each verticil with three branches which
by communicating ramules form a loose irregular wickerwork. Similar to
_Pteroscenium pinnatum_, Pl. 53, figs. 14-16, but without a regular
lattice-shell. A short basal central rod separates two equal (pectoral)
spines from two unequal spines, the larger of the latter is the apical, the
shorter the caudal spine.
_Dimensions._--Length of the apical spine 0.26, of the three basal spines
0.17.
_Habitat._--Central Pacific, Station 274, surface.
{927}3. _Periplecta monocyrtis_, n. sp.
Spines of nearly equal size and shape, cylindrical, irregularly branched.
The apical spine is straight, more branched and nearly twice as long as the
three basal spines. All four spines in the basal third connected by a loose
spongy framework, approaching the form of some Monocyrtida.
_Dimensions._--Length of the apical spine 0.24, of the basal spines 0.13.
_Habitat._--Central Pacific, Station 274, surface.
Subfamily 3. HEXAPLECTICA, Haeckel.
_Definition._--#Plectanida# with six radial spines.
Genus 398. _Hexaplecta_,[17] Haeckel, 1881, Prodromus, p. 425.
_Definition._--#Plectanida# with six radial spines, arising from one common
central point.
The genus _Hexaplecta_ has probably been derived from _Hexaplagia_ by
concrescence of the meeting branches of the six spines, and therefore has
to it the same relation that _Plectophora_ bears to _Plagiacantha_. The two
species here described represent perhaps two different genera, since in the
first all six spines are equal, opposed in pairs, in the second different
in pairs (three upper smaller and three lower larger).
1. _Hexaplecta triaxonia_, n. sp.
Spines equal, opposite in three crossed pairs, straight, three-sided
prismatic, thorny, in the distal half with three leaf-shaped, dentate
edges, in the basal half with three verticils of slender branches, which
are connected by parallel threads, and so form an arachnoidal network with
rectangular or rhomboidal meshes.
_Dimensions._--Length of the spines 0.22, of their basal branches 0.06.
_Habitat._--South Pacific, Station 285, depth 2375 fathoms.
2. _Hexaplecta tricladonia_, n. sp.
Spines unequal, three larger spines (in the lower half of the body) being
opposite to three smaller spines (in the upper half). The latter are nearly
horizontally expanded, each bearing three straight divergent branches. The
larger are stronger, twice as long and armed with three verticils, each of
three branches. All six spines are slender, three-sided prismatic. Their
branches are very thin, thread-shaped, and form by their union a loose
network with irregular polygonal meshes.
_Dimensions._--Length of the larger spines 0.25, of the smaller 0.12.
_Habitat._--South Pacific, Station 291, surface.
{928}Genus 399. _Plectanium_,[18] Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plectanida# with six radial spines, arising in two opposite
divergent groups from the two poles of a common central rod.
The genus _Plectanium_ has been derived from _Plagonium_ by concrescence of
the meeting branches, and bears therefore to it the same relation that the
preceding _Hexaplecta_ exhibits to _Hexaplagia_. Whilst in these two latter
genera the six spines arise from a common central point, they arise here in
two divergent groups from the two poles of a horizontal common middle rod,
similar to the spicula of many #Beloidea#.
1. _Plectanium trigeminum_, n. sp. (Pl. 91, fig. 11).
Spines straight and stout, six to eight times as long as the common middle
rod, three-sided prismatic; in the distal half thickened, with three
divergent terminal thorns; in the basal half with three to four verticils
of thin lateral branches, which are again ramified, and by their united
threads produce an irregular loose framework.
_Dimensions._--Length of the spines 0.25, basal breadth 0.005, terminal
breadth 0.02; length of the middle rod 0.03.
_Habitat._--North Pacific, Station 244, surface.
2. _Plectanium ovodimare_, n. sp.
Spines straight and stout, three-sided prismatic, about four times as long
as the common middle rod, gradually thinned towards the distal end; in the
basal half with two to three verticils of forked branches, which are
dichotomously ramified, and by their united threads form a loose ovate
framework.
_Dimensions._--Length of the spines 0.17, of the middle rod 0.04.
_Habitat._--North Pacific, Station 236, surface.
3. _Plectanium sphærozoum_, n. sp.
Spines straight, cylindrical, ten to twelve times as long as the common
middle rod, with six to eight verticils of thorny branches, tapering
towards the distal end; the branches of the verticils are simple in the
distal half, again ramified in the basal half, and here connected together
by irregularly branched threads forming a loose framework. (Resembles one
spiculum of _Sphærozoum verticillatum_, Pl. 4, fig. 7, but is more richly
branched, with united ramules.)
_Dimensions._--Length of the spines 0.2, of the middle rod 0.01.
_Habitat._--Central Pacific, Station 266, surface.
{929}Subfamily 4. POLYPLECTIDA, Haeckel, 1881, Prodromus, p. 424.
_Definition._--#Plectanida# with numerous (seven to nine or more) radial
spines.
Genus 400. _Polyplecta_,[19] Haeckel.
_Definition._--#Plectanida# with numerous (seven to nine or more) radial
spines, arising from a common centre and lying in different planes.
The genus _Polyplecta_ comprises provisionally all Plectanida possessing
seven or more radial spines, united in the centre of the framework. It may
be derived from _Polyplagia_ by meeting and concrescence of the free
branches. But as in the latter genus, here also the few observed species
are very different, perhaps of different origin, and may be afterwards
better separated as representatives of diverse genera.
1. _Polyplecta heptacantha_, n. sp. (Pl. 91, fig. 12).
_Heptaplegma heptacantha_, Haeckel, 1882, MS.
Seven unequal spines divergent from one common central point, slender,
slightly curved, three-sided prismatic. Four spines are much larger, twice
to three times as long and as thick as the three smaller spines. One of the
four larger spines is directed upwards (as "apical horn"), whilst the three
others diverge downwards (as "basal feet"). Each of the four larger spines
bears five to seven equidistant verticils of three divergent branches, the
proximal of which are branched, the distal simple. The three smaller spines
lie nearly horizontally, midway between the odd apical spine and the three
basal spines, and in the same meridian planes with them; each bears one
verticil of three divergent branches. All the branches are united by
arachnoidal threads, composing a loose wickerwork with irregular, generally
quadrangular meshes.
_Dimensions._--Length of the four larger spines 0.27 to 0.33, of the four
smaller 0.1 to 0.14.
_Habitat._--Central Pacific, Station 271, surface.
2. _Polyplecta enneacantha_, n. sp.
_Enneaplegma enneacantha_, Haeckel, 1881, Prodromus, p. 425.
Nine equal and equidistant, straight, cylindrical radial spines, lying
nearly in one plane, arise from an irregular spongy central framework; six
of them seem to be secondary, intercalated between three equidistant
primary spines, which are united in the centre. (This species resembles in
the nine-radial structure the remarkable _Enneaphormis rotula_, Pl. 57,
fig. 9, and may perhaps be derived from a similar species; but it has no
regular latticed shell.)
_Dimensions._--Length of the spines 0.22, diameter of the framework 0.17.
_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.
{930}3. _Polyplecta decacantha_, n. sp.
_Pentaplegma decacantha_, Haeckel, Prodromus, p. 425.
Ten radial spines, curved, cylindrical, irregularly branched, diverge in
different directions and seem to arise in pairs from an irregular central
framework, in the centre of which five primary spines are united; the
latter correspond probably to the five spines of _Pentaspyris_, &c. The
density of the spongy central framework did not allow of an accurate
investigation, and makes it doubtful whether this species is not a
_Spongiomma_.
_Dimensions._--Length of the spines 0.3 to 0.4, diameter of the framework
0.18.
_Habitat._--Tropical Atlantic, Station 338, depth 1990 fathoms.
4. _Polyplecta polybrocha_, Haeckel.
? _Acanthodesmia polybrocha_, Haeckel, 1865, Zeitschr. f. wiss. Zool.,
Bd. xv. p. 368, Taf. xxvi. fig. 3.
_Plegmosphæra polybrocha_, Haeckel, 1881, Prodromus, p. 455.
Numerous (twenty to thirty or more) radial spines, thin, cylindrical,
curved and irregularly branched, arising from an irregular central spongy
framework, are connected by numerous slender arches. The specimen observed
by me in 1880 in Portofino was a true _Polyplecta_, with three primary
spines centrally united, between which numerous other spines were
intercalated. The similar specimen, however, observed in 1864 in
Villafranca, and figured, _loc. cit._, was perhaps a _Plegmosphæra_.
_Dimensions._--Length of the radial spines 0.05 to 0.1, diameter of the
framework 0.16.
_Habitat._--Mediterranean (Villafranca, Portofino), surface.
5. _Polyplecta dumetum_, Haeckel.
_Acanthodesmia dumetum_, J. Müller, 1868, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 30, Taf. i. Fig. 3.
Numerous (ten to twelve or more) radial spines, thin and straight, with a
few straight lateral branches, diverge in different directions and are
connected by a few slender curved arches. Some similar forms, but more
developed, with numerous branches and curved rods, are found in the Pacific
Radiolarian ooze, and represent probably different species.
_Dimensions._--Length of the radial spines 0.05 to 0.08, of the branches
0.02 to 0.03.
_Habitat._--Mediterranean, French shore (Cette and Saint Tropez), Johannes
Müller, surface.
{931}----
Suborder III. STEPHOIDEA, Haeckel.
_Stephoidea_ vel _Stephida_, Haeckel, 1881, Prodromus, p. 444.
_Acanthodesmida_ (_sensu ampliori_), Bütschli, 1882, Zeitschr. f. wiss.
Zool., vol. xxxvi. p. 495.
_Definition._--NASSELLARIA without complete lattice-shell, with a skeleton
composed of one or more simple rings, which may be united by a loose
framework and are separated by large openings or gates. One primary or
sagittal ring, determining the sagittal or median plane of the bilateral
body, encloses the monaxonian central capsule.
The suborder #Stephoidea#, hitherto known by a few species only of
"Acanthodesmida," comprises a large number of interesting NASSELLARIA (now
more than two hundred species), which possess peculiar interest for the
morphology and phylogeny of this legion. The monaxonian central capsule of
the #Stephoidea# is surrounded either by one simple ring or by a complex
system of several loosely connected rings; these may be united by a loose
framework of connected branches, but never produce a complete
lattice-shell, as is constantly the case in the #Spyroidea#, #Botryodea#,
and #Cyrtoidea#. Therefore there remain between the parts of the connected
rings a few large openings which we call "gates," separating them from the
numerous small "pores" of the complete lattice-shells. In the most simple
case, if only one ring be formed, there is also present only one "gate,"
the aperture of this simple ring.
The first known species of #Stephoidea# were observed in the Mediterranean
by Johannes Müller in 1856, and described and figured in his last treatise
(1858) under the names _Lithocircus annularis_ (_loc. cit._, Taf. i. fig.
1) and _Acanthodesmia vinculata_ (_loc. cit._, Taf. i. figs. 4-7). In the
following year I myself observed two other living species in the
Mediterranean, and described them in my Monograph (1862, pp. 268, 270) as
_Zygostephanus mülleri_ (Taf. xii. fig. 2) and _Prismatium tripleurum_
(Taf. iv. fig. 6). For these four longest known #Stephoidea# I founded the
new family of Acanthodesmida (_loc. cit._, p. 265), but united with them
two other similar genera which I afterwards separated:--_Plagiacantha_
(belonging to the #Plectoidea#) and _Dictyocha_ (belonging to the
PHÆODARIA).
When, in 1876, I received the rich material of the Challenger collection, I
was astonished to find in it an enormous number of new, similar, and partly
very interesting "Acanthodesmida," which were afterwards arranged in my
Prodromus (1881, p. 444) in thirty-eight different genera and four
"subfamilies," all united in one single large family, "Stephida or
Monopylaria cricoidea." I retain here this natural group in the same sense,
but give to it the rank of a "suborder," separating at the same time its
four subfamilies as substantial "families." Since the names of the
{932}latter, proposed in the Prodromus, were not quite suitable, I replace
them here by the following more convenient names:--
1. Family Stephanida (= Monostephida, 1881, p. 447). Skeleton entirely
formed by one simple ring (the primary vertical sagittal ring). The only
"gate" is the simple aperture of the ring.
2. Family Semantida (= Dyostephida, 1881, p. 446). Skeleton composed of
two rings, perpendicular to one another; the primary vertical sagittal
ring bears at the base a horizontal basal ring; between the two rings two
or more "basal gates remain."
3. Family Coronida (= Triostephida, 1881, p. 445). Skeleton composed of
two crossed vertical or meridional rings, perpendicular to one
another--the primary sagittal ring and the secondary frontal ring.
Commonly the two vertical rings are united at the base by a horizontal
basal ring, and between them remain two or more "basal gates."
4. Family Tympanida (= Parastephida, 1881, p. 446). Skeleton composed of
two parallel horizontal rings, and upper mitral ring, and a lower basal
ring, both connected by vertical or divergent columellæ, which are parts
of vertical rings (primary sagittal, and secondary frontal ring).
The peculiar structure of the central capsule of the #Stephoidea#, and
their character as true MONOPYLEA, were first recognised by Richard
Hertwig, who in 1879, in his Organismus der Radiolarien, gave an excellent
detailed description of it (_loc. cit._, pp. 68-72, Taf. vii. figs. 4, 5).
He also pointed out the near affinity of these "Acanthodesmida" with the
#Spyroidea# or Zygocyrtida, uniting the latter with the former family.
A fuller explanation of this affinity, and of the morphological and
phylogenetic importance of the "Acanthodesmida," as ancestral forms of the
#Spyroidea# and #Cyrtoidea#, was given in 1882 by Bütschli (Zeitschr. f.
wiss. Zool., vol. xxxvi. pp. 495-501). He described in detail some
important fossil forms of Acanthodesmida as different species of
"_Stephanolithis_," a name which Ehrenberg had employed for various
ring-like fragments of Radiolarian shells, sponges, and other fossil
bodies. The four fossil species which Bütschli described represent four
different genera of #Stephoidea#, viz., _Semantis_ (_spinescens_),
_Semantrum_ (_mülleri_), _Semantidium_ (_haeckelii_), and _Tristephanium_
(_hertwigii_). On the phylogenetic conclusions, derived from these accurate
observations, compare above, p. 893, &c. The topographical signification of
the parts, employed by Bütschli, is contrary to mine; he calls my dorsal
side the "anterior," and my ventral side the "posterior."
The geometrical fundamental form of the body in nearly all #Stephoidea#
(with few exceptions) is distinctly bilateral or "dipleuric," so that we
can easily distinguish the {933}three different dimensive axes: the
principal axis with different apical and basal poles, the sagittal axis
with different dorsal and ventral poles, and the lateral axis with
equivalent right and left poles. In only a few genera this bilateral
symmetry is not expressed, and a simpler, more regular fundamental form
appears. The latter may be either primary (in the monaxonian _Archicircus_
and _Lithocircus_) or secondary, afterwards acquired (in the octahedral
_Trissocircus_ and _Trissocyclus_, the cubical _Lithocubus_, the prismatic
_Eutympanium_, and some other forms).
The most important element of the skeleton, with which the formation
begins, in all #Stephoidea# is the simple primary or sagittal ring, lying
vertically in the sagittal or median plane of the body and surrounding the
monaxonian central capsule. This sagittal ring is the only essential
element of the skeleton in all Stephanida, and is completely preserved in
all Semantida, also in the greater part of the Coronida and Tympanida. It
is partially reduced in the small groups of the true Acanthodesmida
(subfamily of Coronida) and the Dystympanida and Eutympanida (subfamilies
of Tympanida). Here only the vertical parts of it are preserved (dorsal and
ventral rod), whilst the horizontal parts are lost (mitral and basal rod).
The sagittal ring lies constantly in the vertical median plane of the body,
and therefore divides the enclosed central capsule into a right and a left
half. It is rarely regular or subregular, commonly dipleuric or distinctly
bilateral, so that we may easily distinguish its dorsal and ventral, apical
and basal parts. The most important of these four parts or "rods" is the
"basal rod" or the inferior part, because here the ring is in closer
connection with the central capsule and its "porous area"; here peculiar
spines or branches are commonly developed, which even on the isolated ring
immediately determine the basal pole. The opposite upper part, or the
"mitral rod," is also often distinguished by the peculiar appendages. The
posterior part, or the "dorsal rod" (the anterior rod, _a_, in the
description of Bütschli), is commonly more straight, often quite vertical.
The opposite anterior part, or the "ventral rod" (the posterior rod, _b_,
of Bütschli), is usually more convex, and often strongly curved or
semicircular.
Whilst this dipleuric or bilateral (commonly obliquely ovate or nearly
triangular) form of the sagittal ring is distinctly preserved in by far the
greater number of #Stephoidea#, it is replaced in some few genera by a more
regular, amphithect, diphragmatic, or biradial form. In this case we may
often suppose a primary regularity to exist, the dorsal and ventral parts
being not yet differentiated, as in _Archicircus_ and _Lithocircus_,
_Zygostephanus_ and _Protympanium_, and perhaps also in some other forms.
But in other cases the regularity is, on the contrary, secondary, being
derived from original bilateral forms.
The rod of the sagittal ring is either cylindrical (with circular
transverse section) or angular (commonly with triangular transverse
section). In nearly all #Stephoidea# (with very few exceptions) branches or
apophyses are developed from the ring, regularly disposed and often of
great morphological importance. Commonly these {934}apophyses are developed
in pairs, growing symmetrically on both sides of the ring. The most
important of these apophyses are:--(1) Basal apophyses, arising from the
basal hole of the ring; (2) mitral apophyses, arising from the apical pole;
(3) dorsal apophyses, arising from the middle of the dorsal rod; and (4)
ventral apophyses, arising from the middle of the ventral rod. The two
former arise in the principal axis, the two latter in the sagittal axis of
the body. Very frequently the latter pair is replaced by two pairs of
transverse branches, one inferior (mandibular) and one superior (orbital).
The apophyses of the ring are either simple or branched, often very large,
richly ramified, and give origin to a number of further products.
Whilst in the Stephanida the primary sagittal ring alone represents the
whole skeleton, it produces in all other #Stephoidea# one or more secondary
rings. The most important of these is the horizontal basal ring, appearing
first in the Semantida (Pl. 92). From the base of the sagittal ring there
arise in the horizontal basal plane two pairs of lateral branches or "basal
apophyses." The curved opposite branches of the corresponding pairs become
united on each side of the primary ring (right and left), and so produce a
second, horizontal ring, perpendicular to the former. This basal ring
encloses two paired basal gates, which are enclosed on the medial side by
the basal rod of the sagittal ring, and on the lateral side by two united
apophyses (_Semantis_, Pl. 92, figs. 1, 2). These two primary basal gates
are of the greatest morphological importance; we call them the "jugular
gates or jugular pores" (in the description of Bütschli, the pores I, _loc.
cit._, p. 498). The dorsal pair of basal apophyses (on their posterior
edge) are the coracal rods, _e_ (rods _e_ of Bütschli); the opposite
ventral pair (on their anterior edge) are the clavicular or furcular rods,
_f_ (rods _e_1 of Bütschli); compare Pls. 92-95, and their explanation.
The skeleton of _Semantis_, the prototype of the Semantida, thus assumes
the characteristic form of a signet-ring. The basal ring enclosing the two
jugular pores corresponds to the seal-plate. It is commonly more or less
horizontal; but often the apophyses descend obliquely (Pl. 92, figs. 1, 2,
13, &c.), more rarely laterally (Pl. 29, fig. 11). The further development
of this typical form is essentially effected by the production of new basal
pores in the horizontal seal-plate. In _Semantrum_ (Pl. 92, figs. 3, 4, 5)
we find already four basal gates. Behind the jugular gates is formed a
second pair, the "cardinal gates" (pores II of Bütschli). These are
enclosed on the anterior margin by the coracal rods (_e_), on the posterior
margin by the scapular rods (_d_), a third pair of basal apophyses, arising
behind the former from the sagittal ring and uniting with them (the rods
_e_2 of Bütschli). Commonly the two posterior, or cardinal gates are much
larger than the two anterior, jugular gates. This characteristic basal
plate of _Semantrum_, with two pairs of basal pores, is of the greatest
morphological importance, as it is inherited in by far the greater number
of the NASSELLARIA, though not so generally as Bütschli supposes. The basal
ring of _Semantrum_ is either more circular {935}or elliptical, or more
polygonal, and is connected with the basal rod of the sagittal ring by
three pairs of radial apophyses, the anterior furcular, the middle coracal,
and the posterior scapular rods.
A third important form of Semantida is _Semantidium_ (Pl. 92, figs. 6, 7).
Here we find three pairs of basal pores in the seal-plate; the third pair,
newly formed, consists of the cervical gates (_e_), bounded in front by the
scapular rods (_d_), behind by a fourth pair of basal apophyses, the
cervical rods.
The basal apophyses of the sagittal ring are not only of great
morphological importance, because they produce by their union three typical
pairs of basal gates or "collar pores," but also because their
prolongations often appear as typical basal feet. The distal prolongations
of the coracal rods appear in _Semantiscus_ (Pl. 92, figs. 16-18) as two
pectoral feet, those of the scapular rods as two tergal feet, whilst the
opposite prolongations of the basal rod of the sagittal ring appear as two
"sagittal feet" (in front an anterior or sternal, and behind a posterior or
caudal foot). In the typical _Cortiniscus_ (Pl. 92, figs. 11-13) only three
feet are developed; an odd caudal and two paired pectoral feet (compare
above, p. 891). The typical basal ring of the Semantida, with its paired
basal gates (_Semantis_), reappears in the majority of the Coronida,
differing from the former in the development of a second vertical ring,
which lies in the frontal plane (perpendicular to the sagittal ring), and
which we therefore call the frontal ring. In only one small group of the
Coronida the basal ring is absent, namely, in the Zygostephanida, and here
the frontal ring appears in the simplest form, as a complete elliptical
meridian ring, crossing the sagittal ring perpendicularly on the two poles
of the main axis (_Zygostephanus_, Pl. 93, figs. 1-4), Four large lateral
gates between the two rings remain open. This form may be derived directly
from the Stephanida in the following way; from both poles of a simple
sagittal ring there arise two opposite lateral apophyses, which in the
frontal plane become curved one towards the other, and united in the poles
of the transverse axis. The basal apophyses would be the coracal rods. But
it is also possible that _Zygostephanus_ was derived from _Semantis_ by the
loss of the furcular rods.
The three typical rings (or the "dimensive rings") of the #Stephoidea#
appear in their most complete form in the subfamily Trissocyclida (Pl. 93,
figs. 7, 13). Here all three rings are undivided and completely developed
in the three dimensive planes, perpendicular one to another. Between them
there remain eight large open gates; the four superior are the four
"lateral gates" of _Zygostephanus_, the four inferior are the four basal
gates of _Semantrum_. The four latter are originally much smaller than the
four former; but in _Trissocircus_ and _Trissocyclus_ (Pl. 93, figs. 10-12)
they reach the same size. Therefore all eight gates are here of equal form
and similar size, and the basal ring, now a true equatorial ring, divides
the two meridional rings into two equal halves.
In the Eucoronida, a third subfamily of Coronida, the sagittal and the
basal rings {936}are complete, but the frontal ring is incomplete, its
basal part being wanting (Pl. 82, figs. 4-6). Therefore we find here six
large gates between the three rings; four upper lateral gates (between the
two crossed vertical rings) and two lower basal gates (between the basal
rod of the sagittal ring and the two halves of the basal ring).
_Eucoronis_, the type of this subfamily, may be derived either directly
from _Semantis_ by development of a frontal ring, or from _Tristephanium_
by loss of the basal part of the frontal ring.
A quite simple basal ring with a single gate, distinguishes the fourth
subfamily of Coronida, the Acanthodesmida (_sensu restricto_), the genera
_Coronidium_ (Pl. 82, figs. 1, 2, 7, 8) and _Acanthodesmia_ (Pl. 93, fig.
5). The horizontal basal ring alone is here complete, whilst both vertical
rings (the sagittal and frontal rings) are incomplete, their basal parts
being wanting. Therefore there are here five gates, four lateral and one
basal. These forms may be derived from _Eucoronis_ by loss of the basal rod
of the primary sagittal ring.
The Tympanida, the fourth family of #Stephoidea#, exhibit another type of
ring structure. Here two parallel horizontal rings are constantly
developed, one on the apical pole, the other on the basal pole of the
sagittal ring. The latter is the same basal ring as in the Semantida and
Coronida. The former is a "mitral ring," developed in the same manner, by
union of two pairs of horizontal lateral branches, which arise on both
sides from the apical rod (or mitral rod) of the sagittal ring. In the
simplest case these two parallel horizontal rings are connected only by the
sagittal ring, which is either complete (_Protympanium_, Pl. 93, fig. 14)
or incomplete (_Parastephanus_, Pl. 93, fig. 21). But commonly also an
incomplete frontal ring is present, so that the two horizontal rings are
connected by four vertical or subvertical rods; two of these "columellæ"
are the dorsal and ventral rods of the sagittal ring, the two others are
the lateral rods of the frontal ring. Between the former and the latter are
sometimes developed two, four, or more accessory columellæ (probably halves
of accessory incomplete diagonal meridian rings). In this way arise the
characteristic "drum-forms" of many Tympanida, in which the two parallel
horizontal rings correspond to the upper and lower rings of a drum, whilst
the connecting vertical columellæ correspond to its parallel lateral rods
(Pl. 83, figs. 1, 2, &c.).
Originally the two horizontal rings of these "drum-shells" are both
bisected by the complete sagittal ring, each provided with two lateral
gates (Protympanida). But in the Eutympanida both rings exhibit one simple
gate only, the apical and the basal rod of the sagittal ring being lost. In
the Paratympanida both rings are closed by a secondary lattice-plate whilst
in the Dystympanida the upper (mitral) ring alone is closed by such a
plate, the lower (basal) ring is open. In some Eutympanida the shell
assumes the strange form of a regular geometrical cube, the twelve edges of
which are represented by thin rods of silex (_Lithocubus_)--its four upper
edges represent the mitral ring, the four lower the basal ring; two
opposite of the four vertical {937}cube-edges are the lateral halves of the
frontal ring, the two other alternate ones are the remaining halves of the
reduced sagittal ring (dorsal and ventral rod) (Pl. 82, fig. 12).
In many Tympanida and Coronida a loose irregular lattice or framework is
developed, which partly closes the large open gates. But this never reaches
the completeness of a true lattice-shell, such as we find in the
#Spyroidea#, #Botryodea#, and #Cyrtoidea#. In by far the greater number of
#Stephoidea# the corners, and partly also the rods, of the shell are armed
with numerous irregular spines, often forked or richly branched. Among
these spines the descending "basal apophyses" possess a peculiar
importance, since by their regular number and disposition they correspond
to the radial rods of the #Plectoidea#, and to the typical "feet" of the
#Spyroidea# and #Cyrtoidea#. The most important of them are the three
cortinar feet (one caudal and two pectoral) of _Cortina_, _Cortiniscus_,
&c. (compare above, p. 891).
_The Central Capsule_ exhibits in the #Stephoidea# the same characteristic
structure as in all other MONOPYLEA, first exactly pointed out by Richard
Hertwig in 1879 (Organismus der Radiol., p. 71, Taf. vii. figs. 4, 5). Its
form is commonly ovate or ellipsoidal, sometimes also lentelliptical or
nearly spherical. It exhibits constantly on the basal pole the porochora or
porous area, and in the basal half the podoconus or pseudopodial cone. From
the surrounding sagittal ring it is separated by a thick jelly-like
calymma, which commonly exhibits numerous zooxanthellæ. The numerous
pseudopodia are commonly branched, with rather rare anastomoses. The
membrane of the central capsule is thick.
_Synopsis of the Families of_ #Stephoidea#.
I. Skeleton composed of the simple vertical sagittal ring
only, without secondary rings, 1. STEPHANIDA.
II. Skeleton composed of two crossed rings, a vertical
sagittal and a horizontal basal ring, 2. SEMANTIDA.
III. Skeleton composed of two crossed vertical meridional
rings (a primary sagittal and a secondary frontal ring),
commonly also with a horizontal basal ring, 3. CORONIDA.
IV. Skeleton composed of two parallel horizontal rings
(upper mitral and lower basal ring), both connected by
a vertical sagittal ring (and often by a vertical
frontal ring), 4. TYMPANIDA.
Family XLVIII. #STEPHANIDA#, Haeckel (Pl. 81).
_Monostephida_, Haeckel, 1881, Prodromus, p. 447.
_Definition_.--#Stephoidea# with a simple sagittal ring, without any
lattice-work.
The family #Stephanida# is the most simple of all #Stephoidea#, and
probably the common ancestral group of this suborder (compare above, p.
933). The skeleton {938}consists of a simple ring only, surrounding the
central capsule, and armed commonly with simple thorns or with larger
branched spines. The branches of these spines are constantly free, never
joining together. Therefore the shell exhibits no trace of fenestration or
lattice-work, no pores or gates, except the simple large gate of the ring
itself. In all other #Stephoidea# we find secondary gates or lattice-work.
The first known form of this family is _Lithocircus annularis_, described
by Johannes Müller in 1858 (Abhandl. d. k. Akad. d. Wiss. Berlin, p. 29,
Taf. i. fig. 1). He observed already the central capsule ("Blase")
surrounded by the circular ring of silex, and the calymma ("Strahlige
Gallert") enveloping the whole body. The peculiar structure of the soft
body, particularly the "area porosa" on the basal pole of the central
capsule, and the pseudopodial cone within it, were first accurately
described by Hertwig (in 1879). A great number of simple rings, similar to
these, were found in the Challenger collection, and are here arranged in
six genera and forty-eight species.
The simple ring of silex, which alone forms the skeleton of the Stephanida,
corresponds to the primary or sagittal ring of the other #Stephoidea#, and
lies therefore vertically in the median or sagittal plane of the body. We
can therefore distinguish on it four different segments, rods or bows, two
of which are more horizontal, two more vertical. The former are one upper
bow or apical rod, and one lower bow or basal rod. The latter are one
posterior bow or dorsal rod, and one anterior bow or ventral rod. Sometimes
each of these four component bows is distinguished by a corner-spine, or by
a pair of divergent branches.
In the two simplest (and probably oldest) genera of Stephanida, in
_Archicircus_ and _Lithocircus_, the dorsal and ventral rods of the ring
are equal and cannot be distinguished; therefore the fundamental form is
here amphithect, diphragmatic, or biradial (the poles of the sagittal axis
being equal). In the four other genera the dorsal rod is more straight
(often vertical) and more or less different from the ventral, convexly
curved rod; therefore the fundamental form is here dipleuric or bilateral,
as in the greater number of all NASSELLARIA (the poles of the sagittal axis
being unequal). The general form of the ring in this latter case is
commonly obliquely ovate or nearly triangular, the basal pole being more
pointed, the apical pole more rounded (Pl. 81).
The rods or bows of the ring are either roundish or cylindrical (with
circular or elliptical transverse section), or they are prismatic or
angular (commonly with triangular transverse section). In the latter case
one edge usually is prominent in the sagittal plane (on the convex outside
of the ring), whilst two other edges diverge laterally on both sides of it.
The inner or concave margin of the ring is commonly smooth.
The inner perimeter of the large gate, enclosed by the ring, is commonly
rounded (elliptical or ovate), rarely angular. However, the outer perimeter
of the ring is {939}nearly always polygonal, with prominent corners, and
usually from these arise thorns or branched spines which are regularly
disposed. Regarding this disposition we may distinguish three cases: A, the
spines lie in the sagittal plane and form a single row, arising from the
median edge; B, the spines lie on both sides of the latter and form two
parallel rows, arising from the two lateral edges; C, the spines represent
a combination of A and B, and are disposed in three rows, two paired rows
arising from the two lateral edges, and an odd middle row between them,
arising from the median edge. The spines are simple, without branches, in
_Archicircus_ and _Zygocircus_; more or less branched in _Lithocircus_ and
_Dendrocircus_. The branches are often richly ramified or arborescent, and
exhibit great variety in size, special form, and direction (compare Pl.
81).
The number and disposition of the spines or groups of spines are usually
constant, and may be employed in the further progress of our knowledge, to
distinguish a number of genera and subgenera. Very commonly (perhaps in the
majority of the Stephanida) we find six groups of spines, an apical group
on the upper rod of the sagittal ring, a basal group on the lower rod (on
the porochora of the central capsule), two ventral groups on the anterior
rod, and two dorsal groups on the posterior rod. In other species we find
four or eight groups instead of six, and sometimes a larger number.
The most important of these apophyses of the ring are the basal spines,
arising from its basal pole, where the porochora of the central capsule
rests upon it. They are often much larger and more branched than the other
spines, and attain a peculiar morphological value in the small subfamily
Cortinida. Here we find three or four regularly disposed "basal spines,"
which may be compared to the typical "basal feet" of the #Cyrtellaria#,
appearing in the majority of #Spyroidea# and #Cyrtoidea#. _Cortina_, one of
the most important NASSELLARIA, bears three typical divergent feet on the
base of the simple ring, two paired anterior or "pectoral feet," and an odd
posterior or "caudal foot." The latter appears as a direct basal
prolongation of the dorsal rod of the ring, and is opposed to an upper
prolongation of the same, which corresponds to the "apical horn" of the
#Cyrtellaria# (Pl. 97, figs. 1-3). As already explained above, these three
basal feet of _Cortina_ possess the highest phylogenetic value, since they
may also be compared with the three primary radial spines of the
#Plectoidea#, and so connect the #Cyrtellaria# and the #Plectellaria#.
_Stephanium_ differs from _Cortina_ in the possession of four basal feet,
an odd anterior or "sternal foot" being added to the three typical feet of
the latter (Pl. 92, figs. 20, 21). Some forms of #Plectoidea#
(_Plagoniscus_, _Plectaniscus_, &c.) seem to be nearly related to these
Cortinida, and may be easily transformed into them by development of a
complete ring, embracing the central capsule. They seem to demonstrate the
near affinity of all these triradiate NASSELLARIA (Pl. 91, figs. 4, 5, 9,
10).
{940}_Synopsis of the Genera of Stephanida._
-------------------------------------------------------------------------
I. Subfamily Lithocircida.
No typical basal feet on the base of the ring (no cortinar feet).
-------------------------------------------------------------------------
Ring diphragmatic or { Ring smooth or thorny,
amphithect; dorsal { without branched spines. 401. _Archicircus_.
and ventral bow {
equal. { Ring armed with branched
{ spines, 402. _Lithocircus_.
Ring dipleuric, { Ring smooth or thorny,
bilateral; dorsal { without branched spines, 403. _Zygocircus_.
and ventral bow {
different. { Ring armed with branched 404. _Dendrocircus_.
{ spines.
-------------------------------------------------------------------------
II. Subfamily Cortinida.
Three or four typical basal feet on the ring (cortinar feet).
-------------------------------------------------------------------------
Three basal feet (and { One caudal and two lateral
an apical horn). { feet, 405. _Cortina_.
Four basal feet (and { Two sagittal and two
an apical horn). { lateral feet, 406. _Stephanium_.
Subfamily 1. LITHOCIRCIDA, Haeckel.
_Definition_.--#Stephanida# without typical basal feet or cortinar feet.
Genus 401. _Archicircus_,[20] n. gen.
_Definition_.--#Stephanida# with a simple amphithect or diphragmatic ring,
smooth or thorny, without branched spines and basal feet.
The genus _Archicircus_ is the most primitive and simplest form of all
#Stephoidea#, and probably the common ancestral form, not only of this
suborder, but of the greater number of all NASSELLARIA (compare above, p.
893). The skeleton consists only of a quite simple sagittal ring, in which
commonly a slight difference of both poles of the main axis (basal and
apical pole) is visible, but no difference between the dorsal and the
ventral bow of the ring. In my Prodromus (1881, p. 447) the species of
_Archicircus_ were disposed partly in the subgenus _Monostephus_, partly in
the genus _Lithocircus_.
Subgenus 1. _Monostephus_, Haeckel, 1881, Prodromus, p. 447.
_Definition._--Ring circular, elliptical, or ovate, without prominent
corners.
1. _Archicircus princeps_, n. sp.
Gate circular. Ring circular, smooth, its transverse section also circular.
The simplest form of all #Stephoidea#.
_Dimensions._--Diameter of the gate 0.05 to 0.08; thickness of the ring
0.006 to 0.008.
_Habitat._--Central Pacific, Stations 265 to 274, depth 2350 to 2925
fathoms.
{941}2. _Archicircus monostephus_, n. sp. (Pl. 83, fig. 17).
Gate circular. Ring circular, with three elegantly denticulate edges (one
outer median and two lateral edges). Transverse section of the ring
triangular.
_Dimensions._--Diameter of the gate 0.06 to 0.08; thickness of the ring
0.01 to 0.008.
_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.
3. _Archicircus ellipsis_, n. sp.
Gate elliptical. Ring elliptical, on the inner margin smooth, on the outer
margin with fifteen to twenty equal, short, simple, or slightly forked
thorns. Transverse section ovate.
_Dimensions._--Diameter of the gate 0.05 to 0.09; thickness of the ring
0.01 to 0.014.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms; also
fossil in Barbados.
4. _Archicircus ovalis_, n. sp.
Gate ovate. Ring elliptical, smooth, with three prominent, slightly
distorted edges, without thorns; in the transverse section triangular.
_Dimensions._--Diameter of the gate 0.08 to 0.12; thickness of the ring
0.006 to 0.009.
_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms.
5. _Archicircus monopylus_, n. sp.
Gate ovate. Ring ovate, thorny, with three distorted edges, in the
transverse section triangular; surface covered with numerous simple small
thorns arising from the three edges.
_Dimensions._--Diameter of the gate 0.1 to 0.15; thickness of the ring 0.01
to 0.012.
_Habitat._--Indian Ocean (Madagascar), Rabbe, surface.
Subgenus 2. _Archistephus_, Haeckel.
_Definition._--Ring polygonal, with four to six or more prominent corners
(and commonly with simple spines arising from the corners).
6. _Archicircus quadratus_, n. sp.
Gate square. Ring square, with three edges and four short simple pyramidal
spines on the four corners, opposite in pairs in two perpendicular
diameters. Transverse section triangular.
_Dimensions._--Diameter of the gate 0.08; thickness of the ring 0.008.
_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.
{942}7. _Archicircus rhombus_, n. sp. (Pl. 81, fig. 7).
Gate rhombic. Ring rhombic, with four prominent edges and four pairs of
short, divergent, pyramidal spines on the four corners, arising from the
lateral edges of the four rods, about as long as the radius of the gate.
_Dimensions._--Diameter of the gate 0.04 to 0.08; thickness of the ring
0.007 to 0.01.
_Habitat._--North Pacific, Station 244, depth 2900 fathoms.
8. _Archicircus duodenus_, n. sp.
Gate square or rhombic. Ring rhombic, with three prominent edges and twelve
stout and straight pyramidal spines, about as long as the radius of the
gate. In each of the four corners are three divergent spines, arising from
the three edges of each two meeting rods.
_Dimensions._--Diameter of the gate 0.08; thickness of the ring 0.012.
_Habitat._--North Atlantic, surface (Rabbe).
9. _Archicircus primordialis_, n. sp. (Pl. 81, fig. 1).
Gate ovate. Ring hexagonal, with three prominent edges and six short
pyramidal thorns at the six corners; the basal thorn is either simple or
forked.
_Dimensions._--Diameter of the gate 0.07; thickness of the ring 0.01 to
0.015.
_Habitat._--Central Pacific, Stations 265 to 274, depth 2350 to 2925
fathoms.
10. _Archicircus hexacanthus_, n. sp. (Pl. 81, fig. 4).
Gate subregular, hexagonal. Ring hexagonal, with three sharp edges and six
equal radial pyramidal spines, arising from the six corners and placed in
the plane of the ring, about as long as the diameter of the gate.
_Dimensions._--Diameter of the gate 0.05 to 0.07; thickness of the ring
0.01.
_Habitat._--South Pacific, Station 295, depth 1500 fathoms.
11. _Archicircus hertwigii_, Haeckel.
_Lithocircus annularis_, R. Hertwig (_non_ J. Müller), 1879, Organismus
der Radiol., p. 69. Taf. vii. fig. 5.
Gate hexagonal, with prolonged main axis. Ring hexagonal, with two
prominent edges and six pairs of equal, short, conical spines, arising from
the two edges of the six rods at the six corners and divergent on each side
of the plane of the ring. The basal spine-pair is doubled, therefore there
are in all fourteen spines.
_Dimensions._--Diameter of the gate 0.05 to 0.07; thickness of the ring
0.005 to 0.006.
_Habitat._--Mediterranean (Messina), Hertwig, surface.
{943}12. _Archicircus triglyphus_, n. sp.
Gate ovate. Ring hexagonal, with three prominent edges and twenty-two to
twenty-four simple curved spines, arising from the six corners and about as
long as the diameter of the gate. In the basal corner arise six to nine
larger spines, protecting the basal pole of the central capsule. From each
of the five other corners arise three spines, diverging from the three
edges.
_Dimensions._--Diameter of the gate 0.07 to 0.11; thickness of the ring
0.008 to 0.011.
_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.
13. _Archicircus sexangularis_, n. sp. (Pl. 81, fig. 12).
Gate hexagonal or subcircular. Ring hexagonal, with two sharp prominent
edges and six pairs of divergent spines, about as long as the radius of the
gate, and arising from the two edges at the six corners. The two apical and
the two basal spines are simple and conical, whilst the eight other spines,
arising in pairs from the two dorsal and the two ventral corners, are
slightly forked.
_Dimensions._--Diameter of the gate 0.06 to 0.08; thickness of the ring
0.01 to 0.015.
_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.
Genus 402. _Lithocircus_,[21] J. Müller, 1856, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 484.
_Definition._--#Stephanida# with a simple amphithect or diphragmatic ring,
armed with branched spines, without typical basal feet.
The genus _Lithocircus_ is the oldest known form of all #Stephoidea#,
founded by J. Müller in 1856 for his _Lithocircus annularis_, the first
species of this suborder described. We retain here this cosmopolitan form
as the typical representative of the genus, which differs from the
preceding _Archicircus_, its ancestral form, in the development of branched
radial spines.
1. _Lithocircus annularis_, J. Müller.
_Lithocircus annularis_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 29, Taf. i. fig. 1.
Gate circular. Ring circular, with four forked or simply branched spines,
opposite in pairs in two diameters, perpendicular one to the other. Spines
with slender curved fork-branches, about as long as the diameter of the
gate. The specimen figured by J. Müller bears a supernumerary fifth spine;
numerous other specimens observed by me exhibited a regular cross of four
spines.
_Dimensions._--Diameter of the gate 0.1 to 0.15; length of the spines 0.01
to 0.18.
_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific,
surface.
{944}2. _Lithocircus quadricornis_, n. sp. (Pl. 81, fig. 9).
Gate square. Ring square, with three sharp denticulate edges, and four
large bunches of richly branched spines on the four corners. In each corner
arise three curved spines, about as long as the diameter of the ring; their
numerous irregular branches are forked and curved like the antlers of deer.
_Dimensions._--Diameter of the gate 0.07; length of the horns 0.06 to 0.09.
_Habitat._--South Pacific, Station 300, depth 1375 fathoms.
3. _Lithocircus decimalis_, n. sp. (Pl. 81, fig. 15).
Gate elliptical. Ring pentagonal, with three prominent edges and five pairs
of branched spines on the five corners. In each corner arise two or three
curved spines, about as long as the radius of the gate, each with two to
four forked branches.
_Dimensions._--Diameter of the gate 0.08; length of the spines 0.03 to
0.05.
_Habitat._--North Atlantic, Station 354, surface.
4. _Lithocircus hexablastus_, n. sp. (Pl. 81, fig. 17).
Gate elliptical. Ring hexagonal, with three prominent edges and six pairs
of branched spines, arising from the six corners. Each of the twelve spines
is short and stout, only half as long as the radius of the gate, and bears
a bunch of ten to twenty short, densely aggregated, conical or horn-like
curved branches.
_Dimensions._--Diameter of the gate 0.1; length of the spines 0.02 to 0.03.
_Habitat._--Central Pacific, Stations 265 to 268, depth 2700 to 2900
fathoms.
5. _Lithocircus crambessa_, n. sp. (Pl. 81, fig. 6).
Gate elliptical or subcircular. Ring hexagonal, with three wing-shaped
distorted edges and six groups of branched spines, arising from the six
corners. In each corner arise three short and stout divergent spines, each
bearing a bunch of numerous short roundish branches like a cauliflower,
scarcely as long as the thickness of the ring.
_Dimensions._--Diameter of the ring 0.1 to 0.12, length of the spines 0.01
to 0.02.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.
6. _Lithocircus tarandus_, n. sp. (Pl. 92, fig. 19).
Gate circular. Ring hexagonal, with three sharp edges and six pairs of
large branched spines, arising from the flat lateral edges on the six
corners. Each of the twelve spines is horizontally expanded, longer than
the diameter of the ring and dichotomously forked like the antlers of a
{945}reindeer. If the lateral ends of the branches of this species become
united in the frontal plane, we get _Microcubus_, the four upper spines
forming the mitral ring, the four middle the equatorial ring, and the four
lower the basal ring.
_Dimensions_.--Diameter of the gate 0.08; length of the spines 0.09.
_Habitat_.--Central Pacific, Station 272, surface.
7. _Lithocircus furcatus_, n. sp.
Gate ovate. Ring ovate, with three sharp prominent edges. The two lateral
edges are smooth. The median edge (in the sagittal plane) bears sixteen to
twenty forked spines (commonly eight dorsal, eight ventral, and four
basal). All the spines are of nearly equal size, slightly curved, and about
half as long as the short sagittal axis of the ring.
_Dimensions_.--Diameter of the gate 0.08 to 0.12; length of the spines 0.03
to 0.04.
_Habitat_.--North Pacific, Station 253, depth 3125 fathoms.
8. _Lithocircus magnificus_, n. sp. (Pl. 81, fig. 16).
Gate ovate or nearly elliptical. Ring ovate, with three prominent edges,
and numerous richly branched spines arising from the three edges. The
specimen figured, which I observed living in the Mediterranean, exhibited
eight bunches of larger spines, three dorsal, three ventral, one apical,
and one basal bunch; the latter much larger than the seven others. Each
bunch was composed of two to four larger and numerous smaller spines, their
branches curved and forked. The ovate purple central capsule, with a
distinct podoconus, filled more than the half of the gate.
_Dimensions_.--Diameter of the gate 0.1 to 0.13; length of the spines 0.05
to 0.15.
_Habitat_.--Mediterranean (Portofino, 1880), Atlantic (Canary Islands),
Station 354, surface.
Genus 403. _Zygocircus_,[22] Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi. p. 496.
_Definition_.--#Stephanida# with a simple dipleuric or bilateral ring,
smooth or thorny, without branched spines and basal feet.
The genus _Zygocircus_ and the following _Dendrocircus_ differ from the two
preceding older genera in the bilaterally symmetrical or dipleuric form of
the sagittal ring. Whilst in _Archicircus_ and _Lithocircus_ the two
sagittal halves or bows of the ring, the dorsal and ventral bow, are equal
(therefore the fundamental form amphithect or diphragmatic), here both bows
become distinctly different; the dorsal bow is constantly more straight
(often vertical), the ventral bow more convex (obliquely ascending). This
dipleuric differentiation is most important, as it is transmitted to the
greater number of NASSELLARIA by heredity.
{946}1. _Zygocircus sagittalis_, n. sp.
Gate ovate. Ring half ovate or nearly triangular, with three curved edges
and three prominent corners, one apical and two basal protuberances. Dorsal
rod vertical, twice as long as the horizontal basal rod. Ventral rod
convexly curved.
_Dimensions._--Diameter of the gate 0.05 to 0.07; height of the tubercles
0.01 to 0.015.
_Habitat._--Central Pacific, Stations 265 to 268, depth 2900 fathoms.
2. _Zygocircus trigonus_, n. sp.
Gate triangular. Ring triangular, with three curved edges and three
prominent corners, which are prolonged into nine divergent conical spines;
three spines arising from the three edges of each corner. Dorsal rod
vertical; ventral and basal rods curved and convergent.
_Dimensions._--Diameter of the gate 0.11 to 0.13; length of the spines 0.01
to 0.015.
_Habitat._--Indian Ocean, Sunda Archipelago (Rabbe), surface.
3. _Zygocircus tetragonus_, n. sp.
Gate ovate. Ring quadrangular, without edges, with four simple conical
spines of different sizes; one smaller apical, one larger basal, and two
equatorial spines of middle size (one dorsal and one ventral). Dorsal and
ventral rod curved.
_Dimensions._--Diameter of the gate 0.04 to 0.06; length of the spines
0.018 to 0.026.
_Habitat._--Tropical Atlantic, Station 338, depth 1990 fathoms.
4. _Zygocircus rhombicus_, n. sp.
Gate rhombic. Ring rhombic, with three prominent edges, and eight short
conical curved spines arising from the lateral edges at the four corners of
the rhombus. The basal and ventral spine are larger than the apical and
dorsal spine; the ventral rod is more curved (with smaller angle) than the
shorter dorsal rod. The medial edge of the ring is smooth, without spines.
_Dimensions._--Diameter of the gate 0.08; length of spines 0.02 to 0.04.
_Habitat._--South Atlantic, Station 335, depth 1425 fathoms.
5. _Zygocircus pentagonus_, n. sp. (Pl. 81, fig. 8).
Gate roundish pentagonal. Ring very thick (about as thick as the radius of
the gate), irregularly pentagonal, with prominent sagittal edge. On both
sides of the latter arise at the five corners five pairs of short simple
irregularly curved spines. The four ventral spines are larger than the four
dorsal, and the two basal spines larger than the eight former, forked. (In
fig. 8 the basal spines are turned upwards.)
_Dimensions._--Diameter of the gate 0.07; length of the spines 0.04 to
0.06.
_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.
{947}6. _Zygocircus hexagonus_, n. sp.
Gate irregularly hexagonal. Ring obliquely hexagonal, thick, without edges,
with six short and stout conical spines on the six corners. The two spines
of the curved ventral rod are longer than the two spines of the straight
dorsal rod. The apical spine is smaller and the basal spine larger than the
four others.
_Dimensions_.--Diameter of the gate 0.07 to 0.09; length of the spines 0.01
to 0.03.
_Habitat_.--North Pacific, Station 241, depth 2300 fathoms.
7. _Zygocircus triquetrus_, n. sp. (Pl. 81, fig. 3).
Gate obliquely ovate. Ring obliquely hexagonal, with three sharp edges and
three short conical spines on each of the six corners. Therefore each
hexagonal edge bears six short radial spines of equal size.
_Dimensions_.--Diameter of the gate 0.04 to 0.08; length of the spines 0.01
to 0.02.
_Habitat_.--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
8. _Zygocircus dodecanthus_, n. sp.
Gate semicircular. Ring semicircular or irregularly hexagonal, without
edges, with twelve short blunt spines, arising in pairs from the six
corners; two apical, two basal, and between them two equatorial corners.
Three pairs of spines remain on the straight dorsal rod, three on the
curved ventral rod.
_Dimensions_.--Diameter of the gate 0.04 to 0.06; length of the spines 0.01
to 0.02.
_Habitat_.--Central Pacific, Stations 263 to 268; depth 2650 to 2900
fathoms.
9. _Zygocircus acacia_, n. sp. (Pl. 81, fig. 5).
Gate obliquely ovate. Ring semi-ovate, with straight dorsal and curved
ventral rod, partly with distorted edges. Six bunches of numerous short and
straight conical spines arise from the ring, one larger bunch (often
trifid) from the apex, two smaller bunches from the dorsal, two from the
ventral rod, and one very large bunch from the base. The six bunches are
often more separated, smaller, and the spines shorter than in the figured
specimen, which passes over into _Dendrocircus_.
_Dimensions_.--Diameter of the gate 0.12 to 0.16; length of the spines,
0.01 to 0.07.
_Habitat_.--Central Pacific, Station 266, depth 2750 fathoms.
10. _Zygocircus polygonus_, n. sp. (Pl. 81, fig. 2).
Gate irregularly roundish or ovate. Ring irregularly polygonal or sometimes
nearly circular, without edges, armed with a single series of ten to
fifteen short pyramidal spines, which are irregularly {948}disposed in the
sagittal plane. The ventral rod is strongly curved, often semicircular, the
dorsal rod less curved or nearly straight.
_Dimensions_.--Diameter of the gate 0.05 to 0.07; length of the spines
0.004 to 0.02.
_Habitat_.--Cosmopolitan--Atlantic, Pacific; also fossil in Barbados.
11. _Zygocircus bütschlii_, n. sp.
_Zygocircus productus_, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi. p. 497.
Gate obliquely ovate. Ring irregularly roundish, semi-ovate or ovate, with
interrupted and distorted edges, and with a large number (ten to twenty or
more) of simple, irregularly formed and asymmetrically disposed spines;
commonly some larger spines at the base.
_Dimensions_.--Diameter of the gate 0.05 to 0.09; length of the spines
0.005 to 0.02.
_Habitat_.--Fossil in Barbados.
12. _Zygocircus productus_, Bütschli.
_Zygocircus productus_, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi p. 496.
_Lithocircus productus_, R. Hertwig, 1879, Organismus d. Radiol., p. 69,
Taf. vii. fig. 4.
Gate obliquely ovate. Ring obliquely ovate, with three complete prominent
edges and with numerous (ten to twenty or more) simple, short conical
spines, arising in three series from the three edges; commonly some smaller
spines at the base.
_Dimensions_.--Diameter of the gate 0.1 to 0.2; length of the spines 0.005
to 0.02.
_Habitat_.--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
Genus 404. _Dendrocircus_,[23] Haeckel, 1881, Prodromus, p. 447.
_Definition_.--#Stephanida# with a simple dipleuric or bilateral ring,
armed with branched spines, without typical basal feet.
The genus _Dendrocircus_ has the same dipleuric or bilaterally symmetrical
form of the sagittal ring as its ancestral genus _Zygocircus_. It differs
from the latter in the development of branched radial spines, and therefore
bears to it the same relation as the amphithect _Lithocircus_ does to the
simpler _Archicircus_.
1. _Dendrocircus quadrangulus_, n. sp.
Gate irregularly quadrangular or nearly semicircular. Ring quadrangular,
edgeless, with four unequal sides; ventral rod more curved and with longer
sides than the dorsal rod. From the four edges arise four strong,
irregularly branched spines, about as long as the diameter of the gate,
{949}with curved branches; the ventral and basal spines larger than the
dorsal and apical spines. Similar to _Lithocircus quadricornis_ (Pl. 81,
fig. 9), but less branched, and with a striking difference between the
shorter dorsal and the longer ventral rod.
_Dimensions._--Diameter of the gate 0.04 to 0.06; length of the spines 0.05
to 0.07.
_Habitat._--North Pacific, Station 256, depth 2950 fathoms.
2. _Dendrocircus dodecarrhiza_, n. sp.
Gate obliquely ovate. Ring irregularly quadrangular, with three prominent
edges. From the latter arise at the four corners twelve divergent,
irregularly branched spines (three in each corner), about as long as the
radius of the gate, with curved branches; the three basal spines larger
than the nine others.
_Dimensions._--Diameter of the gate 0.08 to 0.1; length of the spines 0.04
to 0.06.
_Habitat._--Indian Ocean (Maldive Islands), surface (Haeckel).
3. _Dendrocircus dodecancistra_, n. sp. (Pl. 81, fig. 11).
Gate obliquely ovate or nearly elliptical. Ring irregularly ovate, with
three distorted edges and six pairs of branched spines. The two ventral
pairs are much more distant than the two dorsal pairs, the ventral rod
being longer and more curved than the dorsal rod. All twelve spines are of
nearly equal size, are more or less curved, about as long as the diameter
of the gate, and each bears six to twelve irregular short branches at the
end.
_Dimensions._--Diameter of the gate 0.07 to 0.08; length of the spines 0.05
to 0.08.
_Habitat._--Tropical Atlantic, Station 342, depth 1445 fathoms.
4. _Dendrocircus arborescens_, n. sp. (Pl. 81, fig. 10).
Gate irregularly roundish or nearly circular. Ring of the same form, with
slight edges and six pairs of elegant arborescent spines (one apical, two
dorsal, two ventral, and one basal pair); the three latter somewhat larger
than the three former. Each tree is larger than the ring, in the basal half
simple, in the distal half forked, each fork-branch with numerous
dichotomous terminal branches.
_Dimensions._--Diameter of the gate 0.06 to 0.08; length of the spines 0.12
to 0.15.
_Habitat._--Central Pacific, Stations 266 to 274, surface.
5. _Dendrocircus elegans_, n. sp. (Pl. 81, fig. 13).
Gate irregularly ovate. Ring thick, ovate, with three denticulate edges and
six bunches of stout, branched and spinulate, curved spines. The four
ventral spines are more distant than the four dorsal, the ventral rod being
more curved than the dorsal. The latter bears above the two apical spines.
The two basal spines are much larger, deeply forked; their four
fork-branches may be compared to the four basal feet of _Stephanium_.
_Dimensions._--Diameter of the ring 0.09 to 0.11; length of the spines 0.03
to 0.06.
_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.
{950}6. _Dendrocircus barbadensis_, n. sp.
Gate irregularly ovate or nearly semicircular. Ring of the same oblique
form, thick, with interrupted and distorted edges, armed with eight to
twelve larger irregularly formed and branched acute spines; between them
numerous conical smaller spines. This common species is very polymorphous
and variable.
_Dimensions._--Diameter of the ring 0.05 to 0.08; length of the spines
0.005 to 0.02.
_Habitat._--Fossil in Barbados.
7. _Dendrocircus stalactites_, n. sp. (Pl. 81, fig. 14).
Gate obliquely ovate. Ring irregularly ovate or roundish, very thick,
without edges, armed with numerous (eight to twelve or more) short and
stout branches, which are shorter than the diameter of the gate,
irregularly disposed and branched, with very numerous clustered blunt
ramules.
_Dimensions._--Diameter of the gate 0.07 to 0.09; length of the spines 0.02
to 0.06.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.
Subfamily 2. CORTINIDA, Haeckel.
_Definition._--#Stephanida# with typical basal feet (or cortinar feet).
Genus 405. _Cortina_,[24] n. gen.
_Definition._--#Stephanida# with a simple dipleuric or bilateral ring,
bearing at the base three divergent feet (one odd caudal and two paired
lateral feet).
The genus _Cortina_ and the following _Stephanium_ represent together the
small but very important group of Cortinida, differing from the simple
Lithocircida in the possession of three typical basal feet, which are
transmitted to the majority of the NASSELLARIA by heredity, and produce
their peculiar triradial structure. They appear therefore as a combination
of the simple ring (_Zygocircus_) with three basal feet (_Plagonium_). One
of these three divergent feet is the odd caudal foot, opposite to the
apical horn; the two others are the paired lateral or pectoral feet. (On
the probable origin and the typical signification of _Cortina_ compare
above, pp. 891-894.)
1. _Cortina tripus_, n. sp. (Pl. 83, fig. 9).
Ring ovate, smooth, or with a few short thorns. Apical horn oblique,
curved, simple, smooth, about as long as the sagittal axis of the ring.
Feet divergent, curved, simple, smooth, about as {951}long as the horn; the
caudal foot shorter than the two pectoral feet. Very variable in form and
size.
_Dimensions._--Height of the ring 0.06 to 0.09, breadth 0.04 to 0.06;
length of the feet 0.05 to 0.1.
_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, surface and in various
depths.
2. _Cortina typus_, n. sp. (Pl. 97, fig. 1).
Ring kidney-shaped or nearly semicircular, with revolute vertical dorsal
rod and strongly curved ventral rod; both rods with two pairs of
spine-bunches. Apical horn nearly straight, thorny, longer than the ring,
directed a little obliquely backwards. Feet slightly curved, of equal
length, two to three times as long as the ring; each armed with few large
bunches of curved spines, which are more developed in the caudal foot than
in the two pectoral feet.
_Dimensions._--Height of the ring 0.14, breadth 0.08; length of the feet
0.2 to 0.3.
_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms.
3. _Cortina conifera_, n. sp.
Ring subcircular, smooth. Apical horn and the three divergent feet of equal
size and similar form, cylindrical, straight, about as long as the ring, at
the distal end thickened, with a dimply cone (similar to _Tripospyris
conifera_ and _Tripospyris eucolpa_, Pl. 84, figs. 4, 7).
_Dimensions._--Height of the ring 0.08, breadth 0.06; length of the feet
0.09.
_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.
4. _Cortina furcata_, n. sp.
Ring elliptical, with three forked horizontal spines (one on the dorsal and
two on the ventral rod). Apical horn and the three divergent feet of equal
size, somewhat longer than the ring, slightly curved, in the distal half
forked.
_Dimensions._--Height of the ring 0.07, breadth 0.05; length of the feet
0.09.
_Habitat._--South Atlantic, Station 332, depth 2200 fathoms. Fossil in
Barbados.
5. _Cortina dendroides_, n. sp.
Ring ovate, with six pairs of branched horizontal spines, three on the
dorsal and three on the ventral rod. Apical horn very large, arborescent,
about as long and as broad as the ring. Feet similar to the horn, also
richly branched, of equal size. All the rods and their branches curved,
with prominent distorted edges.
_Dimensions._--Height of the ring 0.13 to 0.17, breadth 0.1 to 0.12; length
of the feet 0.15 to 0.2.
_Habitat._--Central Pacific, Stations 266 to 274, depth 2350 to 2925
fathoms.
{952}6. _Cortina cervina_, n. sp. (Pl. 92, fig. 21).
Ring ovate, with four pairs of forked horizontal spines (two dorsal and two
ventral pairs). Apical horn straight and stout, as long as the ring, with
trifid point. Three feet equal, widely divergent, very large, branched like
a deer's antler, with very numerous short and stout, curved and pointed
branches. All rods and branches roundish, without edges.
_Dimensions._--Height of the ring 0.1, breadth 0.07; length of the feet
0.12 to 0.16.
_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.
Genus 406. _Stephanium_,[25] n. gen.
_Definition._--#Stephanida# with a simple dipleuric or bilateral ring,
bearing at the base four divergent feet (two sagittal and two lateral
feet).
The genus _Stephanium_ differs from the preceding nearly allied _Cortina_
in the production of four basal feet; the new foot, missing in the latter,
is the anterior or sternal foot. Therefore _Stephanium_ may be regarded as
the archetype of all those NASSELLARIA in which, on the base of the
sagittal ring, there are developed four typical feet--two sagittal feet
(the posterior caudal and anterior sternal foot) and two lateral feet
(right and left). On the origin of _Stephanium_ compare above, p. 893, &c.
1. _Stephanium quadrupes_, n. sp. (Pl. 92, fig. 20).
Ring ovate, with three prominent dentate edges and a short pyramidal apical
horn. Four feet all of nearly equal size, about as long as the ring, also
with three thorny edges, in the upper half divergent, in the lower
convergent.
_Dimensions._--Height of the ring 0.12, breadth 0.08; length of the feet
0.11 to 0.13.
_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.
2. _Stephanium tetrapus_, n. sp.
Ring elliptical, without edges, thorny, with a stout, thorny apical horn of
the same length. Four feet curved and irregularly branched, divergent, of
different size. The two sagittal feet (the anterior sternal and posterior
caudal) about as long as the ring. The two lateral feet (right and left)
nearly twice as long, more richly branched.
_Dimensions._--Height of the ring 0.16, breadth 0.11; length of the feet
0.15 to 0.3.
_Habitat._--Central Pacific, Station 272, depth 2600 fathoms. Fossil in
Barbados.
{953}Family XLIX. #SEMANTIDA#, n. fam.
_Definition._--#Stephoidea# with a single vertical ring (the primary
sagittal ring), bearing on its base a horizontal ring (basal or cortinar
ring) with two to four or more basal gates (or cortinar pores).
The family #Semantida# differs from the preceding Stephanida in the
development of a small horizontal ring on the base of the primary vertical
sagittal ring. By the crossing of these two rings a small latticed basal
plate is formed, with one or two pairs of pores; rarely with a greater
number of "basal pores." The production of this characteristic "basal
plate" is of the greatest morphological importance, as the beginning of the
numerous different lattice-formations, which are differentiated in the
great majority of NASSELLARIA.
In my Prodromus (1881, p. 446) I had enumerated the Semantida with three
genera (Nos. 298 to 300) as a separate subfamily of the Dyostephida or
"Stephoidea biannularia," and characterised these "Dyostephanida" by the
following definition: "Skeleto annulis duobus composito, qui in duobus
planis invicem perpendicularibus jacent; altero annulo (sagittali)
verticali, altero (basali) horizontali." As the names there given were
already employed with another signification, and as the Zygostephanida
(there united with the Dyostephanida) are more closely related to the
Coronida, I now change the names, and propose to call the family Semantida,
expressing by this term the typical similarity of the skeleton to a
signet-ring (_Semantis_, _Semantrum_, _Semantidium_).
At about the same time, some #Stephoidea# of this family were accurately
described by Bütschli (1882, Zeitschr. f. wiss. Zool., vol. xxxvi. p. 495,
Taf. xxxii. figs. 6, 7, 8). He called them _Stephanolithis_, a name which
Ehrenberg had employed, not for complete shells of Radiolaria, but for
isolated parts of such, and for siliceous fragments of different skeletons,
needles of Sponges, &c. The three species described by Bütschli represent
three different genera of our Semantida, viz., _Semantis spinescens_ (with
two gates in the basal plate), _Semantrum mülleri_ (with four gates), and
_Semantidium haeckelii_ (with six gates). He pointed out the great
morphological value of the fenestrated basal plate and its paired gates, as
beginnings of numerous other NASSELLARIA. But his opinion, that in all
#Spyroidea# and #Cyrtoidea#, derived from these, two pairs of basal gates
were constant, was erroneous, nor was the formation of the first pair
naturally explained; he supposed that the formation of the basal plate
begins by development of an odd sagittal apophysis, arising from the base
of the primary sagittal ring. But this odd sagittal apophysis ("der unpaare
mediane Kieselfortsatz c1", _loc. cit._, p. 497) is in reality not a
primary {954}and essential part of the skeleton, but secondary and of
little morphological value, absent in the majority of the Semantida and of
the other NASSELLARIA.
We divide our family Semantida into two different subfamilies, which
possibly possess a direct phylogenetic relation to the two subfamilies of
Stephanida:--The Semantiscida have no typical feet, and have arisen
directly from the Lithocircida; the Cortiniscida, however, possess the
three typical basal feet of _Cortina_, and may therefore be derived
directly from the Cortinida. Since these three cortinar feet are probably
identical with the three primary radial rods of the #Plectoidea#, an
immediate affinity also to these NASSELLARIA is indicated.
The Semantiscida, which do not possess these three basal cortinar feet, are
the simpler forms of the family. The simplest of all, and perhaps the
common ancestral form of the whole family, is _Semantis_ (Pl. 92, figs. 1,
2). It may be derived from _Archicircus_ or _Zygocircus_ by development of
two pairs of horizontal apophyses on its base, around the porochora of the
central capsule. The two rods of each side (right and left), becoming
curved one towards the other, and meeting laterally, form a simple
horizontal gate, and the two paired basal gates together, a horizontal ring
or basal ring, to which the primary sagittal ring is perpendicular. In the
next allied genus, _Semantrum_ (Pl. 92, figs. 3-5), three pairs of
horizontal apophyses are developed, and therefore two pairs of basal gates
produced, an anterior and a posterior. In the third genus, _Semantidium_
(Pl. 92, figs. 6, 7), three pairs of basal pores or gates are visible,
surrounded and separated by four pairs of horizontal apophyses, which arise
from the base of the sagittal ring. Finally, in _Clathrocircus_ (Pl. 92,
figs. 8-10) the number of apophyses is much increased, and two parallel
rows of pores are developed along the two sides of the sagittal ring.
The basal plate or the "seal," developed from the base of the primary
sagittal ring or "signet-ring," is therefore a horizontal ring, which
becomes bisected by the latter, and exhibits either one pair of primary
"basal gates" or two or three pairs of these important basal pores, rarely
more. Since these pores possess the greatest morphological value, and are
probably everywhere homologous, we give to them and to the separating
apophyses certain names, and call the anterior pair of gates, "jugular
pores" (_i_ in our figures, the pair I of Bütschli); the middle (usually
the largest) pair, "cardinal pores" (_k_ in our figures, the pair II of
Bütschli), and the posterior, smaller pair, "cervical pores," _l_. The
typical pairs of rods, by the union of which these basal pores arise, are
the following:--(1) the clavicular or furcular rods, _f_, the first pair
(rods _e_1 of Bütschli), (2) the coracal rods, _e_, between the jugular and
cardinal pores (rods _e_ of Bütschli), (3) the scapular rods, _g_, between
the cardinal and cervical pores (rods _e_2 of Bütschli), (4) the cervical
rods, the fourth pair of apophyses, the most posterior, _h_. Bütschli
supposes that the topographical succession of the three typical pairs of
basal pores is also the chronological succession, the jugular being formed
first, the {955}cardinal second and the cervical pores third but it seems
that this succession is often altered and that the cardinal pores (the
largest), appear first, the jugular pores (in front of them) second and the
cervical pores third (or perhaps sometimes in the inverse succession).
The Cortiniscida, the second subfamily of Semantida, differ from the
preceding Semantiscida in the possession of three typical basal feet, which
are probably inherited from the Cortinida, and perhaps indirectly from the
Plagonida (_Plagoniscus_). The simplest and the most important form of this
second family is _Cortiniscus_ (Pl. 92, figs. 11-13), differing from its
probable ancestral form, _Cortina_, in the development of a basal ring,
produced by horizontal union of the basal apophyses. The three typical feet
are the same as in all triradiate NASSELLARIA, two paired pectoral feet
(_p__{1}, _p__{11}) diverging on the anterior base of the sagittal ring,
whilst the odd caudal foot (_c_) lies on its posterior base in the sagittal
plane and appears as a basal prolongation of the dorsal rod of the sagittal
ring; the upper part of the dorsal rod is usually prolonged into an
ascending apical horn. In _Stephaniscus_ (Pl. 92, figs. 14, 15) four basal
feet are visible, an anterior or sternal foot (_z_) being added as a
prolongation of the basal rod of the ring, opposite to the caudal foot.
Finally, _Semantiscus_ (Pl. 92, figs. 16-18) is distinguished by the
possession of six divergent basal feet, probably identical with those of
all six-radiate NASSELLARIA; three of these may be regarded as primary and
perradial, the odd caudal and the paired pectoral feet; the three other
intercalated as secondary or interradial feet, the odd sternal (_z_) and
the paired tergal feet (_t__{1}, _t__{11}).
The basal plate of these Cortiniscida exhibits the same important
differences as in the preceding Semantiscida, either one, or two, or three
pairs of basal gates being developed. But there occur also in some species
(mainly in _Cortiniscus_) only three basal gates, an odd anterior (between
the two pectoral feet and a connecting horizontal bar), and two paired
posterior (between the two pectoral and the odd caudal foot). It requires
further accurate researches to solve the important problem, what the true
homologies of these typical basal pores and the separating bars are in the
different genera of Semantida. In _Semantiscus_ there are three pairs of
basal pores in the horizontal seal, corresponding to those of _Semantidium_
and the radial rods or bars between, these are the basal parts of the six
radial feet; therefore the odd caudal foot (_t_) seems to be the posterior,
and the odd sternal foot (_z_) the anterior prolongation of the basal part
of the primary sagittal ring; the two paired anterior or pectoral feet
(_p__{1}, _p__{11}) the prolongations of the coracal rods (_e_) and the two
paired posterior or tergal feet (_t__{1}, _t__{11}), the prolongations of
the scapular rods (_g_). But it is not yet certain whether these six radial
feet and the separating gates of the basal plate are all the same and truly
homologous in all six-radiate NASSELLARIA. In every case the comparative
study of the Semantida is of the highest value for the accurate knowledge
of the MONOPYLEA.
{956}_Synopsis of the Genera of Semantida._
-------------------------------------------------------------------------
I. Subfamily Semantiscida.
Basal ring without typical, regularly disposed basal feet
(no cortinar feet).
-------------------------------------------------------------------------
{ Two basal pores, 407. _Semantis_.
Only two, four, or six {
basal pores (no dorsal { Four basal pores, 408. _Semantrum_.
and ventral pores). {
{ Six basal pores, 409. _Semantidium_.
Besides four basal pores, also apical pores or
dorsal and ventral pores along the whole ring, 410. _Clathrocircus_.
-------------------------------------------------------------------------
II. Subfamily Cortiniscida.
Basal ring with typical, regularly disposed basal feet
(cortinar feet).
-------------------------------------------------------------------------
{ One odd caudal foot and
Three basal feet. { two paired lateral
{ feet, 411. _Cortiniscus_.
{ Two sagittal and two
Four basal feet. { lateral or pectoral
{ feet, 412. _Stephaniscus_.
{ Two sagittal, two
Six basal feet. { pectoral, and two
{ tergal feet, 413. _Semantiscus_.
Subfamily 1. SEMANTISCIDA, Haeckel.
_Definition._--#Semantida# without typical basal feet or cortinar feet.
Genus 407. _Semantis_,[26] n. gen.
_Definition._--#Semantida# with two basal pores (or jugular pores), without
typical basal feet.
The genus _Semantis_, the most primitive and the oldest of the Semantida,
is of the greatest morphological interest, as the first form of
#Stephoidea# which produces gates or pores by communicating branches, and
therefore the probable ancestral form not only of this family, but of the
greater number of all #Stephoidea#, and perhaps even of all #Spyroidea# and
#Cyrtoidea#. _Semantis_ arises from _Archicircus_ by the production of two
pairs of lateral branches from the basilar rod of the sagittal ring, one
anterior pair of clavicular rods, and one posterior pair of coracal rods.
By junction of the clavicular and coracal rod on each side arises a left
and a right pore, the "jugular pore or jugular gate."
1. _Semantis biforis_, n. sp. (Pl. 92, fig. 2).
Sagittal ring obliquely ovate, nearly trapezoidal, with six pairs of short
mammillated knobs or branches; dorsal rod straight, vertical, with two
pairs of knobs, ventral rod strongly convex, also with {957}two pairs of
knobs; two other pairs in the apical rod. Basilar rod horizontal, straight.
Basal ring with six pairs of similar knobs, three on each side. Basal gates
ovate or nearly triangular.
_Dimensions._--Height of the sagittal ring 0.09, breadth 0.07.
_Habitat._--Central Pacific, Stations 265 to 268, depth 2700 to 2900
fathoms.
2. _Semantis distoma_, n. sp.
Sagittal and basal ring nearly of the same form as in the preceding
species, but half as thick and armed with numerous branched spines which
are about half as long as the diameter of the main gate, and with thin and
curved pointed branches.
_Dimensions._--Height of the sagittal ring 0.11, breadth 0.08.
_Habitat._--North Pacific, Station 244, depth 2900 fathoms.
3. _Semantis dipyla_, n. sp.
Sagittal ring kidney-shaped, very thick, with six pairs of short, thorny,
or irregularly tuberculated knobs (two dorsal, two apical, and two ventral
pairs). Basal ring smooth, scarcely half as thick, horizontal, with two
semicircular basal gates, about half as broad as the main gate. From the
two opposite lateral corners of the basal ring two slender upwardly curved
spines arise, resembling the basal part of a commencing frontal ring.
_Dimensions._--Height of the sagittal ring 0.08, breadth 0.05.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.
4. _Semantis sigillum_, n. sp. (Pl. 92, fig. 1).
Sagittal ring elliptical, with four pairs of stout arborescent spines (two
apical and two equatorial pairs), which are irregularly branched and
forked, with numerous thin lateral branches. Apex with a short conical
trifid vertical horn. Basal ring thorny, with obliquely descending slightly
curved bars.
_Dimensions._--Height of the sagittal ring 0.12, breadth 0.09.
_Habitat._--South Pacific, Station 300, depth 1375 fathoms.
5. _Semantis distephanus_, n. sp. (Pl. 83, fig. 3).
Sagittal ring thin, semicircular, smaller than the thin basal ring, which
exhibits two semicircular gates. Both rings are armed with numerous small
spines of equal size, which on the former are arranged in two, on the
latter in three regular rows. (The basal rod of the sagittal ring,
separating the two basal gates, in fig. 3 is, by mistake, not distinctly
enough drawn.)
_Dimensions._--Height of the sagittal ring 0.06, breadth 0.08.
_Habitat._--Tropical Atlantic, Station 348, surface.
{958}6. _Semantis spinescens_, Haeckel.
_Stephanolithis spinescens_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p.160, Taf. i. fig. 29.
_Stephanolithis spinescens_, Bütschli, 1882, Zeitschr. f. wiss. Zool.,
vol. xxxvi. p. 497, Taf. xxxii. figs. 7_a_, 7_b_.
Sagittal ring ovate with four pairs of thin, irregularly branched spines,
two apical pairs, one on the straight dorsal rod and one on the curved
ventral rod. Basilar rod with a posterior and an anterior forked rod
(commencing caudal and sternal foot). Basal ring square, with two lateral
spines, and two triangular gates scarcely one-third as broad as the
ring-gate. An internal ascending procolumna (rod _c__1 in the figure of
Bütschli) connects the basal and ventral rods of the sagittal ring.
_Dimensions._--Height of the sagittal ring 0.1, breadth 0.07.
_Habitat._--Fossil in Barbados.
Genus 408. _Semantrum_,[27] n. gen.
_Definition._--#Semantida# with four basal pores (two anterior jugular and
two posterior cardinal pores), without typical basal feet.
The genus _Semantrum_, one of the most important of the NASSELLARIA, arises
from the preceding _Semantis_ by duplication of the two basal gates. Behind
the pair of coracal rods there arises from the basilar rod of the sagittal
ring a third pair of lateral horizontal branches, the scapular rods. These
become connected with the coracal rods on each side, and so produce a
second posterior pair of basal pores, the "cardinal gates." These are
constantly larger than the anterior "jugular gates." Therefore the vertical
ring of _Semantrum_ possesses a horizontal basal ring with four very
characteristic gates, enclosed by three pairs of lateral curved and
connected branches, and these become transmitted by heredity to the
majority of the NASSELLARIA.
1. _Semantrum quadrifore_, n. sp. (Pl. 92, fig. 5).
Sagittal ring subcircular or ovate, with three edges and four sagittal
forked spines on the odd edge (two dorsal and two ventral spines). Basal
ring decagonal, with ten simple or forked spines on the ten corners.
Jugular gates tetragonal. Cardinal gates pentagonal.
_Dimensions._--Height of the sagittal ring 0.09, breadth 0.07.
_Habitat._--Tropical Atlantic, Station 351, surface.
{959}2. _Semantrum tetrastoma_, n. sp. (Pl. 92, fig. 3).
Sagittal ring semicircular, thorny, without edges. Basal ring tetragonal or
nearly cordate, with a small anterior and a large posterior bow-shaped
incision; on the lateral edges with numerous irregular thorns. Jugular
gates pear-shaped. Cardinal gates nearly kidney-shaped.
_Dimensions._--Height of the sagittal ring 0.1 to 0.14, breadth 0.07 to
0.09.
_Habitat._--Central Pacific, Stations 265 to 268, depth 2700 to 2900
fathoms.
3. _Semantrum tetrapylum_, n. sp.
Sagittal ring elliptical, tuberculate. Basal ring trapezoidal, also with
roundish thick rods and small irregular tubercles on the margin. Jugular
gates ovate, two-thirds as broad as the triangular cardinal gates.
_Dimensions._--Height of the sagittal ring 0.08, breadth 0.05.
_Habitat._--North Pacific, Station 253, depth 3125 fathoms.
4. _Semantrum mülleri_, Haeckel.
_Stephanolithis mülleri_, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi pp. 499, 539, Taf. xxxii. figs. 8_a_, 8_b_, 8_c_.
Sagittal ring nearly semicircular or obliquely ovate, thorny. Basal ring
also nearly semicircular, with two slight sagittal incisions (one anterior
and one posterior), on the lateral edges with numerous small thorns.
Jugular pores (pair I of Bütschli) pear-shaped. Cardinal pores (pair II of
Bütschli) triangular. Sometimes (but not constantly) a pair of cervical
bows connects the scapular bars with the subvertical dorsal rod of the
sagittal ring.
_Dimensions._--Height of the sagittal ring 0.09, breadth 0.06.
_Habitat._--Fossil in Barbados.
5. _Semantrum sphragisma_, n. sp.
Sagittal ring circular, smooth. Basal ring also nearly circular and smooth;
its four basal gates of nearly equal size, elliptical or subcircular; the
jugular pores scarcely smaller than the cardinal pores. All rods smooth,
cylindrical, without edges and thorns.
_Dimensions._--Height of the sagittal ring 0.08, breadth 0.07.
_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms; also fossil
in Barbados.
6. _Semantrum bütschlii_, n. sp.
Sagittal ring triangular, with vertical straight ascending dorsal rod,
horizontal straight basilar rod and obliquely ascending, slightly curved
ventral rod; all rods nearly cylindrical, with irregular {960}branched
thorns and distorted edges. Jugular pores triangular, scarcely half as
broad as the large semicircular cardinal pores.
_Dimensions._--Height of the sagittal ring 0.11, breadth 0.08.
_Habitat._--Fossil in Barbados.
7. _Semantrum signarium_, n. sp. (Pl. 92, fig. 4).
Sagittal ring obliquely ovate, thorny. Basal ring kidney-shaped or nearly
pentagonal, with broad concave dorsal incision and five larger branched
spines on the five corners; between them smaller thorns. Jugular gates
pear-shaped, scarcely half as broad as the triangular cardinal gates.
_Dimensions._--Height of the sagittal ring 0.12, breadth 0.09.
_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.
Genus 409. _Semantidium_,[28] n. gen.
_Definition._--#Semantida# with six basal pores (two anterior jugular, two
middle cardinal, and two posterior cervical pores), without typical basal
feet.
The genus _Semantidium_ exhibits a further developmental stage of the basal
plate of the Semantida. Whilst this plate in _Semantis_ possesses one pair
of basal pores, and in _Semantrum_ two pairs, here in _Semantidium_ it has
three pairs. The new third pair is produced on the dorsal edge of the basal
plate, which becomes connected with the basal part of the dorsal rod of the
sagittal ring by a pair of cervical rods. The middle pair of pores (the
cardinal) are always larger than the anterior (jugular) and the posterior
(cervical pores). The same form of basal plate is preserved in numerous
#Spyroidea# and #Cyrtoidea#, as a "cortinar septum with six collar pores,"
(_e.g._, Pl. 53, fig. 18).
1. _Semantidium hexastoma_, n. sp. (Pl. 92, fig. 6).
Sagittal ring ovate, thorny. Basal ring rhombic or nearly square, with four
short conical descending spines on the four prominent edges (two sagittal
and two lateral); between them numerous smaller irregular thorns. Jugular
and cervical gates nearly equal, ovate, half as broad as the triangular
cardinal gates between them.
_Dimensions._--Height of the sagittal ring 0.14, breadth 0.1.
_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.
2. _Semantidium sexangulum_, n. sp.
Sagittal ring ovate, with six pairs of short branched thorns (two apical,
two dorsal, and two ventral). Basal ring hexagonal, with three pairs of
short branched thorns on the six corners (one {961}sagittal pair, one
posterior and one anterior). All six gates of the basal plate triangular,
the jugular and cervical a little smaller than the cardinal gates.
_Dimensions._--Height of the sagittal ring 0.1, breadth 0.07.
_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms.
3. _Semantidium haeckelii_, Bütschli.
Stephanolithis Haeckelii, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol.
xxxvi. pp. 499, 538, Taf. xxxii. figs. 6_a_, 6_b_.
Sagittal ring elliptical, with three pairs of short horizontal branched
spines, one apical and two equatorial pairs (one dorsal and one ventral).
Basal ring roundish hexagonal, with numerous short thorns on the margin.
Jugular pores ovate, about half as broad as the ovate cardinal pores and
twice as broad as the small cervical pores.
_Dimensions._--Height of the sagittal ring 0.08, breadth 0.06.
_Habitat._--Fossil in Barbados.
4. _Semantidium signatorium_, n. sp. (Pl. 92, fig. 7).
Sagittal ring semicircular, thorny; basal ring pentagonal, with short
spines on the margin and five stronger thorny spines on the five corners.
Jugular pores ovate, smaller than the triangular cervical pores. Cardinal
pores two to three times as large as each of the former, pentagonal.
_Dimensions._--Height of the sagittal ring 0.08, breadth 0.12.
_Habitat._--North Pacific, Station 341, depth 2300 fathoms.
Genus 410. _Clathrocircus_,[29] Haeckel, 1881, Prodromus, p. 447.
_Definition._--#Semantida# with a variable number of pores on the apical
and the basal part of the ring, symmetrically arranged, without typical
basal feet.
The genus _Clathrocircus_ comprises those Semantida in which the sagittal
ring bears not only basal pores (as in the three preceding genera) but also
apical pores (on the opposite pole of the main axis), or a variable number
of pores along the whole ring. All these pores are symmetrically arranged
in pairs. In the simplest form there are only two apical pores opposite to
four basal pores, whilst in the highest state of development the whole ring
bears two complete circles of pores. At both poles of the transverse axis
two large lateral gates remain open. If these become closed by
lattice-work, _Clathrocircus_ passes over into _Dictyospyris_.
{962}1. _Clathrocircus hexaporus_, n. sp.
Sagittal ring circular, smooth, with three pairs of pores (one apical and
two basal). The two apical pores are triangular with two lateral spines,
and correspond to the two mitral gates of the Tympanida. The four basal
pores form a hexagonal basal plate, with six lateral spines, and correspond
to the four basal pores of _Semantrum_; the two jugular are pear-shaped,
and half as broad as the two triangular cardinal pores.
_Dimensions._--Height of the sagittal ring 0.08, breadth 0.06.
_Habitat._--Cosmopolitan; Atlantic, Pacific, many Stations, surface.
2. _Clathrocircus octoporus_, n. sp.
Sagittal ring elliptical, smooth, with four pairs of pores (two apical and
two basal). The four apical pores are of nearly equal size, subcircular,
and form a regular cross around the apical pole. The four basal pores are
ovate, and form a quadrangular plate, armed with marginal thorns; the two
jugular pores are somewhat smaller than the two cardinal pores.
_Dimensions._--Height of the sagittal ring 0.11, breadth 0.08.
_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms.
3. _Clathrocircus decaporus_, n. sp.
Sagittal ring ovate, thorny, with five pairs of pores (two apical and three
basal). The four apical pores are roundish and form a cross. The six basal
pores are triangular and form a hexagonal plate with thorny margin; the two
jugular pores are somewhat larger than the two cervical, and half as broad
as the two cardinal pores.
_Dimensions._--Height of the sagittal ring 0.09, breadth 0.07.
_Habitat._--North Pacific, Station 256, depth 2950 fathoms.
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