_Definition._--Ring with six chambers, separated by six radial beams.
9. _Archidiscus hexoniscus_, n. sp. (Pl. 48, figs. 10, 10_a_).
Ring regular, hexagonal, or nearly circular, connected with the central
chamber by six radial beams of equal length and at equal distances (60°);
therefore all six chambers of the same size and form. (Resembles the
central part of the disk of _Hexinastrum geryonidum_, Pl. 44, fig. 4.)
_Dimensions._--Diameter of the ring 0.06, of the central chamber 0.018.
_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.
10. _Archidiscus pyloniscus_, n. sp. (Pl. 48, figs. 11, 11_a_).
Ring triangular, connected with the central chamber by six radial beams at
alternating distances; therefore three larger chambers (of looser network)
alternate with three smaller chambers (of denser network); pores of the
former twice to three times as large as those of the latter. This species
is of peculiar importance, as an immediate transitional form to the
Pylodiscida. If these three larger ring chambers lose their few
lattice-beams and so became open gates, we get _Triolene_ or _Triopyle_,
the original forms of the Pylodiscida.
_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.015.
_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.
{489}11. _Archidiscus hexathalamus_, n. sp.
Ring irregular, roundish, or hexagonal, connected with the central chamber
by six radial beams of unequal increasing length; therefore all six ring
chambers of gradually increasing size (beginning a spiral convolution,
original form of some _Discospira_).
_Dimensions._--Diameter of the ring 0.05 to 0.07, of the central chamber
0.014.
_Habitat._--South Pacific, Station 300, depth 1375 fathoms.
Subgenus 6. _Circoniscus_, Haeckel.
_Definition._--Ring with seven or more chambers, separated by seven or more
radial beams.
12. _Archidiscus octoniscus_, n. sp.
Ring circular or regular octagonal, connected with the central chamber by
eight equidistant radial beams; therefore eight ring chambers of equal
size. (Compare the central part of the disk of _Porodiscus quadrigatus_,
Pl. 41, fig. 3.)
_Dimensions._--Diameter of the ring 0.04, of the central chamber 0.014.
_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.
13. _Archidiscus polythalamus_, n. sp.
Ring circular, connected with the central chamber by nine to ten or more
radial beams at nearly equal distances. Ring chambers nine to ten, more or
less equal, sometimes also eleven to twelve, more different. (This species
is very variable, and may perhaps be divided into a number of different
"transformistic species.")
_Dimensions._--Diameter of the ring 0.04 to 0.06, of the central chamber
0.015.
_Habitat._--Central Pacific, Stations 265 to 274, depths 2350 to 2925
fathoms.
Genus 213. _Axodiscus_,[252] n. sp.
_Definition._--#Porodiscida# with a simple central chamber, surrounded by
one single concentric ring, which is divided by radial beams into two to
six or more radial chambers; margin of the disk armed with radial spines.
The genus _Axodiscus_ differs from the preceding _Archidiscus_ only in the
shape of the margin of the small lenticular disk, which is armed with a
variable number of radial spines, indicating certain axes or radii of the
shell. If these marginal spines at certain equal distances from the margin
branch and their distal ends become united by these branches forming a
concentric second ring, the genus passes into _Porodiscus_. The different
number and disposition of the marginal spines are probably very important,
{490}as determining the later development of two to four or more radii in
the different genera of Porodiscida.
1. _Axodiscus stylophorus_, n. sp.
Ring circular, with two equal semicircular chambers, connected with the
central chamber by two opposite radial beams, which are prolonged outside
into two strong conical spines.
_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.016.
_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.
2. _Axodiscus triradiatus_, n. sp.
Ring regular, triangular, equilateral, connected with the central chamber
by three equidistant radial beams, which are prolonged outside into three
short conical spines. (Differs from _Archidiscus trioniscus_ in the
possession of marginal spines.)
_Dimensions._--Diameter of the ring 0.04, of the central chamber 0.013.
_Habitat._--Central Pacific, Station 267, depth 2700 fathoms.
3. _Axodiscus staurophorus_, n. sp.
Ring regular, square, connected with the central chamber by four radial
beams, which lie opposite in pairs in two perpendicularly crossed axes, and
are prolonged outside into four delicate cylindrical spines.
_Dimensions._--Diameter of the ring 0.045, of the central chamber 0.015.
_Habitat._--North Pacific, Station 244, depth 2900 fathoms.
4. _Axodiscus hexagonus_, n. sp.
Ring regular, hexagonal, connected with the central chamber by six radial
beams at equal distances, which are prolonged outside into six strong
pyramidal spines.
_Dimensions._--Diameter of the ring 0.06, of the central chamber 0.018.
_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.
5. _Axodiscus trigonus_, n. sp.
Ring regular, triangular, equilateral, connected with the central chamber
by six radial beams of alternating length and distance; therefore three
smaller (perradial) chambers (with denser and darker network) alternating
with three larger (interradial) chambers (with looser and finer network).
On the margin three strong conical radial spines, arising in the radius of
the larger chambers. (Differs from _Archidiscus pyloniscus_, Pl. 48, fig.
11, mainly in the strong angular spines on the three corners of the
triangular shell.)
_Dimensions._--Diameter of the ring 0.05, of the central chamber 0.014.
_Habitat._--South Pacific, Station 296, depth 1825 fathoms.
{491}6. _Axodiscus octogonus_, n. sp.
Ring circular or nearly octagonal, connected with the central chamber by
eight radial beams at nearly equal distances, which are prolonged outside
into eight short conical spines. (Differs from _Archidiscus octoniscus_ in
the marginal prolongation of the eight beams.)
_Dimensions._--Diameter of the ring 0.04, of the central chamber 0.013.
_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.
7. _Axodiscus spinosus_, n. sp.
Ring circular, connected with the central chamber by ten to twelve radial
beams at nearly equal distances, which are prolonged outside into short
conical spines of variable length. (May be regarded as an aculeate variety
of _Archidiscus polythalamus_.)
_Dimensions._--Diameter of the ring 0.04 to 0.05, of the central chamber
0.014.
_Habitat._--Central Pacific, Stations 265 to 274, depths 2350 to 2950
fathoms.
Subfamily 2. TREMATODISCIDA, Haeckel, 1862, Monogr. d. Radiol., p. 491
(_sensu emendato et restricto_).
_Definition._--#Porodiscida# without radial appendages of the disk (solid
spines or chambered arms on the margin), and without peculiar oscula on the
margin of the disk, which is composed of two to four or more concentric
rings.
Genus 214. _Porodiscus_,[253] Haeckel, 1881, Prodromus, p. 459.
_Definition._--#Porodiscida# with simple circular disk, composed of several
rings (without radial appendages or peculiar oscula on the margin of the
disk).
The genus _Porodiscus_ is, next to its ancestral form, _Archidiscus_, the
simplest and most primitive form of the Porodiscida, from which all other
genera of this family can be derived. The disk is quite simple, without any
marginal appendages, composed of a variable number of rings, commonly of
circular form, sometimes more or less polygonal, elliptical, or irregular.
In my Monograph (1862, pp. 491, 513) I had separated the species, here
united in _Porodiscus_, into two different genera: _Trematodiscus_ with
concentric rings, and _Discospira_ with spiral rings. But the extended
study of these very common forms in a great number of specimens in the
Challenger collection has convinced me that the separation of those two
genera cannot be maintained. In one and the same locality, where one single
characteristic disk-form is very common, we find intermingled quite regular
disks with only concentric, circular rings (_Trematodiscus_), and other
disks with one single perfect spiral ring (_Discospira_); and between
{492}these a smaller number of specimens, in which the rings of the disk
are partly concentric, partly spiral; either the rings of the central part
of the disk are concentric, the outer spiral (_Perispira_), or the
proportion is inverse (_Centrospira_); and sometimes the whole disposition
of the concentric and spiral rings is irregular, and the rings often
interrupted (_Atactodiscus_). Therefore it appears more natural to give to
all these different forms only the value of subgenera of _Porodiscus_, as I
have already proposed in my Prodromus (1881, p. 459). Even the numerous
species of _Porodiscus_ (mainly characterised by the equal or different
breadth of the rings, and by the number, form, and size of the connecting
radial beams and of the superficial pores) are for the most part very
variable and hard to distinguish, as all those characters are not constant.
_Porodiscus_ is a quite "transformistic genus."
Subgenus 1. _Trematodiscus_, Haeckel, 1860, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 841.
_Definition._--All rings of the disk concentric (commonly circular, rarely
a little elliptical or polygonal).
1. _Porodiscus orbiculatus_, Haeckel.
_Trematodiscus orbiculatus_, Haeckel, 1862, Monogr. d. Radiol., p. 492,
Taf. xxix. fig. 1.
_Trematodiscus orbiculatus_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 108.
All rings of the disk circular, concentric, of equal breadth, connected by
numerous alternating radial beams. Chambers differing little in size, about
as large as the central chamber. Pores regular, circular, two to two and a
half on the breadth of each ring.
_Dimensions._--Diameter of the disk (with nine rings) 0.18; breadth of each
ring 0.01; pores 0.003.
_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific,
surface; also fossil in Tertiary rocks of Barbados, Sicily, and Nicobar.
2. _Porodiscus concentricus_, Haeckel.
_Trematodiscus concentricus_, Haeckel, 1862, Monogr. d. Radiol., p. 493.
_Trematodiscus concentricus_, Stöhr, 1880, Palæontogr., vol. xxvi. p.
108.
_Flustrella concentrica_, Ehrenberg, 1838, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 132; _Ibid._, 1875, p. 72, Taf. xxii. fig. 13.
? _Flustrella concentrica_, Ehrenberg, 1854, Mikrogeol., Taf. xix. fig.
61, Taf. xx. fig. 42, Taf. xxi. fig. 51, Taf. xxxvi. fig. 29.
All rings of the disk circular, concentric, of equal breadth, connected by
numerous piercing radial beams. Chambers different in size, increasing
from the centre towards the periphery. Pores regular, circular, one and
half to two on the breadth of each ring.
_Dimensions._--Diameter of the disk (with eight rings) 0.16; breadth of
each ring 0.01; pores 0.003.
_Habitat._--Fossil in many Tertiary rocks--Barbados, Sicily, Greece, &c.
_Porodiscus haeckelii_ = _Trematodiscus haeckelii_, Bütschli, 1882, L. N.
41, Taf. xxiv. figs. 5_a_, 5_b_.
{493}3. _Porodiscus flustrella_, n. sp. (Pl. 41, fig. 1).
_Trematodiscus flustrella_, Haeckel, 1866, MS. Canar. Ins.
All rings of the disk circular, concentric, of equal breadth, connected by
numerous piercing radial beams. Chambers different in size, increasing from
the centre towards the periphery. Pores very irregular, polygonal, or
roundish, one to three on the breadth of each ring.
_Dimensions._--Diameter of the disk (with six rings) 0.12; breadth of each
ring 0.01; pores 0.002 to 0.006.
_Habitat._--Cosmopolitan; Atlantic, Pacific, &c., many Stations, surface.
4. _Porodiscus sorites_, Haeckel.
_Trematodiscus sorites_, Haeckel, 1862, Monogr. d. Radiol., p. 492, Taf.
xxix. fig. 2.
All rings of the disk circular, concentric, of equal breadth, connected by
numerous alternating radial beams. Chambers different in size, increasing
from the centre. Pores regular, circular, one to one and a half on the
breadth of each ring.
_Dimensions._--Diameter of the disk (with six rings) 0.12; breadth of each
ring 0.01; pores 0.006.
_Habitat._--Mediterranean (Messina), surface.
5. _Porodiscus macroporus_, Haeckel.
_Trematodiscus macroporus_, Haeckel, 1879, MS.
_Flustrella macropora_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 160.
All rings of the disk circular, concentric, of equal breadth, connected by
numerous piercing radial beams. Chambers of different breadth, increasing
from the centre. Pores regular, very large, nearly square, one single pore
on the breadth of each ring.
_Dimensions._--Diameter of the disk (with five rings) 0.11; breadth of each
ring 0.01; pores 0.005.
_Habitat._--Fossil in the Tertiary rocks of Barbados.
6. _Porodiscus microporus_, Haeckel.
_Trematodiscus microporus_, Stöhr, 1880, Palæontogr., vol xxvi. p. 108,
Taf. iv. fig. 17.
All rings of the disk concentric, either circular or a little elliptical;
the innermost rings of the same breadth as the central chamber, the third
ring much broader. Radial beams between them alternating; chambers of
different size. Pores very small, subregular, everywhere of the same size,
four to five pores on the breadth of each ring.
_Dimensions._--Diameter of the disk (with three rings) 0.15; breadth of the
inner rings 0.02, of the outer 0.03; pores 0.0016.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
{494}7. _Porodiscus ellipticus_, Haeckel.
_Trematodiscus ellipticus_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 108,
Taf. iv. fig. 16.
All rings of the disk concentric, either circular or a little elliptical,
connected by eight piercing radial beams; central chamber elliptical, of
the same breadth as the first ring, broader than the following rings, the
breadth of which decreases towards the periphery. Pores irregular, in the
inner rings twice as broad as in the outer (third) ring, four to five on
the breadth of each ring.
_Dimensions._--Diameter of the disk (with three rings) 0.18; breadth of the
inner rings 0.03, of the outer 0.02; pores 0.003 to 0.006.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
8. _Porodiscus heterocyclus_, Haeckel.
_Trematodiscus heterocyclus_, Haeckel, 1862, Monogr. d. Radiol., p. 493,
Taf. xxix. fig. 3.
? _Flustrella cyclia_, Harting, 1863, Fauna Banda-Zee, p. 11, pl. i. fig.
19.
_Trematodiscus heterocyclus_, Stöhr, 1880, Palæontogr., vol. xxvi. p.
108.
All rings of the disk concentric, circular, connected by numerous radial
beams, which are partly piercing, partly alternating. The breadth of the
rings increases gradually from the centre towards the periphery,
corresponding also to the size of the pores; two to three circular pores on
the breadth of each ring.
_Dimensions._--Diameter of the disk (with six rings) 0.17; breadth of the
second ring 0.007, of the sixth 0.02; pores 0.002 to 0.006.
_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface; also
fossil in Tertiary rocks of Barbados and the Mediterranean.
9. _Porodiscus quadrigatus_, n. sp. (Pl. 41, fig. 3).
All rings of the disk concentric, of nearly equal breadth, connected by
four interradial beams, perpendicular one to another. The first ring
(surrounding the central chamber) with eight chambers, the second only with
four (alternating with the four radial beams). Size of the four chambers of
each ring increases much towards the periphery. Pores regular, circular,
about two on the breadth of each ring.
_Dimensions._--Diameter of the disk (with six rings) 0.18; breadth of each
ring 0.05; pores 0.004.
_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms.
Subgenus 2. _Perispira_, Haeckel, 1881, Prodromus, p. 459.
_Definition._--The inner rings of the disk concentric (commonly circular);
the outer rings spirally convoluted.
{495}10. _Porodiscus perispira_, n. sp. (Pl. 41, fig. 2).
_Perispira perforata_, Haeckel, 1881, Prodromus.
Inner rings of the disk (two or three) concentric, outer rings (three or
four) spirally convoluted, spiral line simple. All rings nearly of the same
breadth, connected by alternating irregular radial beams. Pores irregular,
two to three on the breadth of each ring.
_Dimensions._--Diameter of the disk (with six rings) 0.17; breadth of each
ring 0.016; pores 0.003 to 0.005.
_Habitat._--Pacific, central area, Stations 272 to 274, surface.
11. _Porodiscus radiatus_, n. sp.
_Perispira radiata_, Haeckel, 1881, Prodromus.
Inner rings of the disk (four or five) concentric, outer rings (three or
four) spirally convoluted, spiral line simple. All rings connected by
piercing radial beams (eight in the inner half, sixteen in the outer half).
Breadth of the rings and of the pores increasing from the centre towards
the periphery, three to four pores on the breadth of each ring.
_Dimensions._--Diameter of the disk (with eight rings) 0.18; breadth of the
second ring 0.006, of the eighth ring 0.02; pores 0.002 to 0.006.
_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.
Subgenus 3. _Centrospira_, Haeckel, 1881, Prodromus, p. 459.
_Definition._--The inner rings of the disk spirally convoluted, the outer
rings concentric (commonly circular).
12. _Porodiscus centrospira_, n. sp. (Pl. 41, fig. 6).
_Centrospira perispongidium_, Haeckel, 1881, Prodromus.
Inner rings of the disk (two or three) spirally convoluted (with simple or
double spiral line), outer rings (three or four) concentric, subcircular.
All rings nearly of the same breadth, connected by alternating radial
beams. Pores subregular, two to three on the breadth of each ring.
Lattice-work in the periphery of the disk a little spongy (as in Pl. 41,
fig. 11).
_Dimensions._--Diameter of the disk (with five rings) 0.15; breadth of each
ring 0.015; pores 0.003.
_Habitat._--Pacific, central area, Station 267, depth 2700 fathoms.
Subgenus 4. _Discospira_, Haeckel, 1862, Monogr. d. Radiol., p. 513.
_Definition._--All rings of the disk spirally convoluted, forming parts of
a simple or double spiral turning.
{496}13. _Porodiscus helicoides_, Haeckel.
_Discospira helicoides_, Haeckel, 1862, Monogr. d. Radiol., p. 514, Taf.
xxix. fig. 7.
_Trematodiscus helicoides_, Haeckel, 1860, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 841.
All rings of the disk spirally convoluted around the central chamber;
spiral line regular, simple. All rings nearly of the same breadth,
connected by numerous alternating radial beams. Chambers little different
in size, little longer than broad. Pores of equal size, regular, two on the
breadth of each ring.
_Dimensions._--Diameter of the disk (with ten rings) 0.2; breadth of each
ring 0.01; pores 0.0025.
_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific; also fossil in
the Tertiary rocks of the Mediterranean, Sicily, Oran, &c.
14. _Porodiscus spiralis_, Haeckel.
_Flustrella spiralis_, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 210; Mikrogeol., 1854, Taf. xix. fig. 62.
_Discospira spiralis_, Haeckel, 1862, Monogr. d. Radiol., p. 513.
All rings of the disk spirally convoluted around the central chamber;
spiral line regular, simple. All rings nearly of the same breadth,
connected by numerous (twelve to sixteen) piercing radial beams. Chambers
increasing in size from the centre towards the periphery. Pores irregular,
of different size, one and a half to two on the breadth of each ring.
_Dimensions._--Diameter of the disk (with eight rings) 0.16; breadth of
each ring 0.01; pores 0.004.
_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific; also
fossil in the Tertiary rocks of Barbados, Sicily, Greece, &c.
15. _Porodiscus operculina_, Haeckel.
_Discospira operculina_, Haeckel, 1862, Monogr. d. Radiol., p. 514, Taf.
xxix. fig. 8.
All rings of the disk spirally convoluted around the central chamber,
spiral line regular, simple. Breadth of the rings and length of the
chambers increasing in size from the centre towards the periphery. Most
part of chambers twice as long as broad. Pores irregular, of very different
sizes, two to three on the breadth of each ring.
_Dimensions._--Diameter of the disk (with six rings) 0.16; breadth of the
rings 0.012 to 0.016; pores 0.002 to 0.006.
_Habitat._--Mediterranean (Messina), surface.
16. _Porodiscus bilix_, Haeckel.
_Discospira bilix_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 113, Taf. vi.
fig. 3.
All rings of the disk spirally convoluted around the large elliptical
central chamber. Spiral convolutions of the inner rings simple, of the
outer rings double; the latter twice as broad as the {497}former. Pores
regular, circular, in the inner rings one pore on the breadth, in the outer
rings two to three pores. Radial beams piercing, numerous, on the margin
prominent.
_Dimensions._--Diameter of the disk (with six rings) 0.14; breadth of the
inner rings 0.007, of the outer 0.013; pores 0.0017.
_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.
17. _Porodiscus bispiralis_, Haeckel.
_Stylodictya bispiralis_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 160. Taf. xxiv. fig. 1.
All rings of the disk spirally convoluted, in a perfect double spiral, with
increasing breadth of the rings; the fourth ring twice as broad as the
first. Pores regular, circular; in the inner rings one pore on the breadth,
in the outer rings two to three pores. Radial beams piercing, numerous,
prominent on the margin.
_Dimensions._--Diameter of the disk (with four rings) 0.1; breadth of the
inner rings 0.006, of the outer 0.012; pores 0.0015.
_Habitat._--Fossil in the rocks of Barbados; living in the depths of the
Central Pacific, Station 268, depth 2900 fathoms.
18. _Porodiscus duplex_, Haeckel.
_Discospira duplex_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 114, Taf.
vi. fig. 4.
All rings of the disk spirally convoluted, in a perfect double spiral, with
increasing breadth of the broad rings. Pores regular, circular; in the
inner rings two to three, in the outer four to five on the breadth. Radial
beams interrupted. Margin of the rings thorny.
_Dimensions._--Diameter of the disk (with three rings) 0.15; breadth of the
rings 0.02 to 0.04; pores 0.007.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
19. _Porodiscus semispiralis_, n. sp. (Pl. 41, fig. 4).
All rings of the disk spirally convoluted, divided by four radial,
perpendicularly crossed and zigzag shaped beams into four quadrants; the
quarter rings of each quadrant halving the rings of each adjacent quarter.
Half spiral line often irregular or partly interrupted. Breadth of all
rings nearly equal. Pores irregular, roundish, two on the breadth of each
ring. Margin of the disk dentated.
_Dimensions._--Diameter of the disk (with nine rings) 0.22; breadth of each
ring 0.012; pores 0.002 to 0.006.
_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.
Subgenus 5. _Atactodiscus_, Haeckel, 1881, Prodromus, p. 459.
_Definition._--Rings of the disk more or less irregular, partly concentric,
partly spirally convoluted, often interrupted.
{498}20. _Porodiscus deformis_, Haeckel.
_Discospira deformis_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 114, Taf.
vi. fig. 6.
Rings of the disk irregular, partly concentric, partly spiral, often
interrupted, increasing in breadth from the centre. Radial beams not
piercing; pores regular, circular, two to six on the breadth of the
different rings. (Very variable and irregular, sometimes more spiral, at
other times more concentric, but always with equal pores.)
_Dimensions._--Diameter of the disk (with four rings) 0.18; breadth of the
first ring 0.014, of the second 0.03, of the fourth 0.06; pores 0.005.
_Habitat._--Fossil in the Tertiary rocks of Barbados and Sicily; living in
the Central Pacific, Stations 266 to 268, depths 2700 to 2900 fathoms.
21. _Porodiscus irregularis_, n. sp. (Pl. 41, fig. 7).
_Atactodiscus irregularis_, Haeckel, 1881, Prodromus, p. 459.
_Perispongidium irregulare_, Haeckel, 1878, MS. et Atlas (pl. xli. fig.
7).
Rings of the disk irregular, partly concentric, partly spiral, often
interrupted, with nearly equal breadth. Radial beams not piercing; pores
irregular, roundish, two to four on the breadth of each ring; network in
the periphery of the disk spongy. (Very variable and irregular, sometimes
more spiral, at other times more concentric; disk in the peripheral part
often more or less spongy. Differs from the preceding by the equal breadth
of the rings and the different size of the pores.)
_Dimensions._--Diameter of the disk (with six rings) 0.15; breadth of each
ring 0.011; pores 0.002 to 0.004.
_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface; also
fossil in Barbados.
Genus 215. _Perichlamydium_,[254] Ehrenberg, 1847, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 54.
_Definition._--#Porodiscida# with a simple circular disk (without radial
spines and chambered arms), surrounded on the margin by a thin porous (but
not chambered) equatorial girdle.
The genus _Perichlamydium_ differs from _Porodiscus_ only in the
development of a thin, porous, equatorial girdle, which surrounds the
circular margin of the chambered disk. This girdle lies in the equatorial
plane of the lenticular disk, and represents a very delicate siliceous
plate, perforated by numerous small pores. Sometimes the proximal part of
the girdle is ribbed by thin radial beams, the distal prolongations of the
radial rods of the central disk. If these ribs reach the margin of the
girdle and are prominent over it, _Perichlamydium_ passes over into
_Stylochlamydium_.
{499}1. _Perichlamydium praetextum_, Ehrenberg.
_Perichlamydium praetextum_, Ehrenberg, 1847, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 21 (non
20).
_Perichlamydium praetextum_, Haeckel, 1862, Monogr. d. Radiol., p. 495.
All rings of the disk (three to four) concentric, circular, of equal
breadth, with interrupted (not piercing) radial beams. Equatorial girdle
without radial beams, nearly as broad as the disk; its circular pores of
the same size as those of the disk; about two pores on the breadth of each
ring.
_Dimensions._--Diameter of the disk (without the girdle, with four rings)
0.11; breadth of each ring 0.012; breadth of the girdle 0.06 to 0.1; pores
0.004.
_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, surface; also fossil
in the Tertiary rocks of Barbados and Sicily.
2. _Perichlamydium saturnus_, n. sp. (Pl. 41, fig. 5).
All rings of the disk (three to four) concentric, circular (sometimes
partly concentric, circular, partly spiral, or irregular), with interrupted
(not piercing) radial beams. Equatorial girdle without radial beams, about
half as broad as the disk; its circular pores very small, scarcely half as
large as those of the disk; about three pores on the breadth of each ring.
(Very variable in the ring-form, differs from the preceding in the small
pores of the girdle.)
_Dimensions._--Diameter of the disk (without the girdle, with three rings)
0.11; breadth of each ring 0.02, pores 0.004, breadth of the girdle 0.05,
pores 0.002.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
3. _Perichlamydium accrescens_, Haeckel.
_Discospira accrescens_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 114,
Taf. vi. fig. 5.
All rings of the disk (six to seven) not concentric, convoluted in a simple
spiral, of nearly equal breadth, with interrupted (not piercing) radial
beams. Equatorial girdle in the proximal part with numerous radial beams,
which do not reach its margin; its pores half as large as those of the
disk, where one to two pores arise on the breadth of each ring. (The girdle
becomes twice to three times as broad as in the figure of Stöhr.)
_Dimensions._--Diameter of the disk (with seven rings, without the girdle)
0.13; breadth of each ring 0.007 to 0.01; pores 0.0036; breadth of the
girdle 0.05, pores of it 0.0017.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stöhr),
Caltanisetta (Haeckel); living in the Central Pacific, Station 266, depth
2750 fathoms.
4. _Perichlamydium spirale_, Ehrenberg.
_Perichlamydium spirale_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 80, Taf. xxii. fig. 12.
All rings of the disk (three to four) not concentric, convoluted in a
simple spiral, of increasing breadth from the centre; connected by numerous
piercing radial beams. Equatorial girdle about {500}half as broad as the
disk, without radial beams; its pores of the same size as those of the
disk, regular, circular; three pores on the breadth of the first ring, six
pores of the fourth ring.
_Dimensions._--Diameter of the disk (with four rings, without the girdle)
0.12; breadth of the first ring 0.01, of the fourth 0.02; breadth of the
girdle 0.05; pores 0.003.
_Habitat._--Fossil in the rocks of Barbados.
Subfamily 3. OMMATODISCIDA, Stöhr, 1880, Palæontographica, vol. xxvi. p.
115.
_Definition._--#Porodiscida# without radial appendages of the
concentrically annulated disk, but distinguished by one single or two
opposite large marginal oscula, or wide openings on the margin of the disk,
armed with a coronet of spines.
Genus 216. _Ommatodiscus_,[255] Stöhr, 1880, Palæontographica, vol. xxvi.
p. 115.
_Definition._--Porodiscida without chambered arms and radial spines on the
margin of the circular or elliptical disk, but with one large marginal
osculum or opening surrounded by a coronet of spines.
The genus _Ommatodiscus_, together with the following _Stomatodiscus_, form
the peculiar small subfamily of Ommatodiscida, founded by Stöhr in 1880
(_loc. cit._). These remarkable Porodiscida, very nearly allied to
_Porodiscus_, are distinguished by one or two large openings on the margin
of the disk, and these "marginal oscula" are constantly armed with a
coronet of spines (comparable to the osculum coronatum of _Sycon_ in the
Calcispongiæ). Probably in the living Ommatodiscida the osculum is the door
from which a "sarcode-flagellum" issues (comp. above, p. 407). Perhaps this
osculum is comparable to the peculiar coronet of spines which is developed
on one pole of the shell axis in some Ellipsida (_Lithomespilus_,
_Lithapium_). The internal structure of the disk is commonly more or less
obscure, as the lenticular disk is much thickened, sometimes nearly
ellipsoidal. It is possible that the Ommatodiscida are more nearly related
to the Lithelida than to the Porodiscida; but there is no indication of an
internal trizonal medullary shell. Also the apparent resemblance to the
Cyrtida is of no morphological value; both groups are of quite independent
phylogenetic origin.
Subgenus 1. _Ommatodiscinus_, Haeckel.
_Definition._--Disk circular.
1. _Ommatodiscus decipiens_, Stöhr.
_Ommatodiscus decipiens_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 115,
Taf. vi. figs. 8, 8_a._
Disk circular, with two chambered rings around the spherical central
chamber, of equal breadth. Chambers twice as high as broad. Pores very
small, one-third as broad as the bars {501}between them, two on the breadth
of each ring. Osculum of the same breadth as the central chamber,
surrounded by numerous very short teeth.
_Dimensions._--Diameter of the disk 0.12; breadth of the central chamber
and of each ring 0.03; pores 0.0015.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
2. _Ommatodiscus stöhrii_, n. sp.
Disk circular with three chambered rings around the spherical central
chamber, of equal breadth. Chambers broader than high. Pores of the same
breadth as the bars between them, four on the breadth of each ring. Osculum
of the same breadth as the central chamber, surrounded by a corona of ten
to twenty thin, bristle-shaped teeth, as long as its diameter.
_Dimensions._--Diameter of the disk 0.2; breadth of the central chamber and
of each ring 0.03; pores 0.004.
_Habitat._--North Pacific, Station 244, depth 2900 fathoms.
3. _Ommatodiscus circularis_, n. sp.
Disk circular, with four circular chambered rings around the spherical
central chamber, of increasing breadth; the fourth ring twice as broad as
the second. Chambers about as broad as high. Pores large, twice as broad as
the bars, one to two on the breadth of each ring. Osculum twice as broad as
the central chamber, surrounded by a coronal of strong conical teeth, twice
as long as its diameter.
_Dimensions._--Diameter of the disk 0.18; breadth of the central chamber
and inner rings 0.015, of the outer rings 0.03; pores 0.01.
_Habitat._--South Pacific, Station 295, depth 1500 fathoms.
Subgenus 2. _Ommatodisculus_, Haeckel.
_Definition._--Disk elliptical.
4. _Ommatodiscus haeckelii_, Stöhr.
_Ommatodiscus haeckelii_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 115,
Taf. vi. figs. 7, 7_a._
Disk elliptical (6 : 7), with four chambered rings around the elliptical
central chamber, of equal breadth. Chambers about as high as broad. Pores
small, half as broad as the bars, two on the breadth of each ring. Osculum
three times as broad as the central chamber, surrounded by a crown of
strong conical teeth.
_Dimensions._--Length of the disk 0.18, breadth 0.16; breadth of each ring
and of the central chamber 0.02; pores 0.003.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stöhr),
Caltanisetta (Haeckel).
{502}5. _Ommatodiscus lævigatus_, Stöhr.
_Ommatodiscus lævigatus_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 116,
Taf. vi. figs. 9, 9_a._
Disk elliptical (3 : 4), with three chambered rings around the circular
central chamber, the third ring half as broad as the second. Chambers twice
as high as broad. Pores very small, one-third as broad as the bars. Osculum
twice as broad as the central chamber, armed with a crown of short conical
teeth.
_Dimensions._--Length of the disk 0.15, breadth 0.11; breadth of inner
rings 0.02, of the outer 0.01; pores 0.0017.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
6. _Ommatodiscus fragilis_, Stöhr.
_Ommatodiscus fragilis_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 116,
Taf. vi. figs. 10, 10_a._
Disk elliptical (4 : 5), with five chambered rings around the elliptical
central chamber, the fifth ring twice as broad as each of the others.
Chambers about as high as broad. Pores very small, one-fifth as broad as
the bars. Osculum three times as broad as the central chamber, surrounded
by a coronet of short teeth.
_Dimensions._--Length of the disk 0.17, breadth 0.13; breadth of the inner
rings 0.01, of the outer 0.02; pores 0.001.
_Habitat._--Fossil in Tertiary rocks of Sicily and Barbados; living in
depths of the Tropical Atlantic and Pacific, Station 353, depth 2965
fathoms, Station 265, depth 2900 fathoms, &c.
Genus 217. _Stomatodiscus_,[256] n. gen.
_Definition._--#Porodiscida# without chambered arms and radial spines on
the margin of the circular or elliptical disk, but with two large,
opposite, marginal oscula, or openings surrounded by a coronet of spines.
The genus _Stomatodiscus_ has the same characteristic structure as the
foregoing _Ommatodiscus_, and differs from it only in the duplication of
the large marginal openings. Whilst in the latter there is only one such
marginal osculum, here we find on the margin of the disk two oscula,
opposite on the poles of one equatorial axis.
1. _Stomatodiscus amphistomus_, n. sp.
Disk circular, with three concentric rings of equal breadth around the
central chamber. Pores irregular, roundish, about two on the breadth of
each ring. Surface of the lenticular shell spiny. On two opposite points of
the margin a large osculum, three to four times as broad as the central
chamber, armed with a coronet of strong pyramidal spines of different
length, the longest equal to the radius of the disk.
{503}_Dimensions._--Diameter of the disk (with three rings) 0.12; breadth
of each ring 0.016; pores 0.004.
_Habitat._--South Pacific, Station 302, depth 1450 fathoms.
2. _Stomatodiscus osculatus_, n. sp. (Pl. 48, fig. 8).
Disk elliptical, nearly twice as long as broad, with three concentric rings
around the elliptical central chamber, one piercing radial beam in the main
axis, the other beams interrupted. Surface of the shell with small
scattered thorns. Pores very irregular, roundish, partly aggregated in
groups of four to eight smaller porules. On both poles of the main axis a
large elliptical marginal osculum, about as large as the central chamber,
armed with a coronet of short conical spines.
_Dimensions._--Length of the disk (with three rings) 0.18, breadth 0.1;
pores 0.001 to 0.006.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.
Subfamily 4. STYLODICTYIDA, Haeckel, 1881, Prodromus, p. 459.
_Definition._--#Porodiscida# with solid radial spines on the margin of the
concentrically annulated disk, situated in the equatorial plane of the disk
(without chambered arms and marginal oscula).
Genus 218. _Xiphodictya_,[257] Haeckel, 1881, Prodromus, p. 460.
_Definition._--#Porodiscida# with two opposite, solid, radial spines on the
margin of the circular or elliptical disk.
The genus _Xiphodictya_ opens the series of the Stylodictyida or of those
Porodiscida in which the margin of the chambered disk is armed with solid
radial spines, all situated in the equatorial plane of the disk.
_Xiphodictya_ exhibits the minimum number of spines, two being opposite on
the poles of one equatorial axis of the disk. It repeats, therefore, in
this family the same amphistylic formation as _Sethostylus_ in the
Phacodiscida and _Stylocyclia_ in the Coccodiscida.
Subgenus 1. _Xiphodictyon_, Haeckel.
_Definition._--All rings of the disk concentric, circular.
1. _Xiphodictya amphibelonia_, n. sp. (Pl. 42, fig. 10).
All rings of the disk concentric, circular, of equal breadth. Pores
irregular, roundish, one and a half to two on the breadth of each ring.
Margin of the disk thorny, of the same thickness as {504}the central part
of the medal-shaped or cylindrical disk. Two opposite radial spines very
long and thin, cylindrical, twice to three times as long as the diameter of
the disk, only half as thick as the breadth of one ring.
_Dimensions._--Diameter of the disk (with five rings) 0.17; breadth of each
ring 0.014; pores 0.003 to 0.012.
_Habitat._--North Pacific, Station 244, depth 2900 fathoms.
2. _Xiphodictya amphirrhopalia_, n. sp. (Pl. 42, fig. 11).
All rings of the disk concentric, circular, with increasing breadth from
the centre; the fifth ring twice as broad as the second. Central chamber
very large. Margin of the lenticular disk thorny, much thinner than the
central part. Pores irregular, roundish, two to three on the breadth of
each ring. Two opposite radial spines club-shaped, about as long as the
diameter of the disk, in the outer spindle-shaped part three to four times
as broad as at the base.
_Dimensions._--Diameter of the disk (with six rings) 0.17; breadth of the
second ring 0.008, of the fifth ring 0.016.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms; also
fossil in the Tertiary rocks of Sicily (Caltanisetta).
Subgenus 2. _Xiphospira_, Haeckel.
_Definition._--All rings of the disk or a part of them not concentric,
spirally convoluted; sometimes irregular or interrupted.
3. _Xiphodictya staurospira_, n. sp. (Pl. 42, fig. 12).
All rings of the disk not concentric, half spiral. Four radial beams,
crossed perpendicularly and zigzag-shaped, divide each ring into four
quadrants; the quarter-ring of each quadrant halves the two adjacent rings.
All rings of equal breadth. Pores irregular, roundish, two on the breadth
of each ring. Two opposite radial spines pyramidal, somewhat shorter than
the diameter of the disk.
_Dimensions._--Diameter of the disk (with six rings) 0.16; breadth of each
ring: 0.014; pores 0.003 to 0.007.
_Habitat._--South Pacific, Station 295, depth 1500 fathoms.
4. _Xiphodictya heliospira_, n. sp.
All rings of the disk not concentric, convoluted in a simple, regular,
spiral line; all nearly of equal breadth. Pores subregular, circular, two
on the breadth of each ring. Two opposite radial spines conical, about as
long as the radius of the disk. Margin of the disk thorny. (Differs from
_Stylodictya heliospira_, Pl. 41, fig. 8, mainly by the two strong,
opposite, radial spines.)
{505}_Dimensions._--Diameter of the disk (with six rings) 0.14; breadth of
each ring 0.01 to 0.012; pores 0.002 to 0.006.
_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.
Genus 219. _Tripodictya_,[258] Haeckel, 1881, Prodromus, p. 460.
_Definition._--#Porodiscida# with three solid, equidistant, radial spines
on the margin of the circular or triangular disk.
The genus _Tripodictya_ exhibits three radial spines on the margin of the
disk, divergent at equal angles; rarely in some specimens the angles differ
more or less. Perhaps this genus bears a near relation to the Dictyastrida
(or to the Euchitonida with three chambered arms--_Dictyastrum_,
_Euchitonia_, &c.).
1. _Tripodictya trigonaria_, n. sp. (Pl. 42, fig. 8).
All rings of the disk concentric, triangular, with three equal convex
sides, all of the same breadth; first and second rings with three simple
chambers, third and fourth rings with six chambers, fifth ring with twelve
chambers. Central chamber also equilateral triangular, from its three
corners arise three piercing perradial beams; from the second ring arise
three interradial beams, alternate with the latter; from the fourth ring
between these and the former arise six adradial beams. Pores subregular,
two on the breadth of each ring. Three marginal spines pyramidal, as long
as the radius of the disk and as broad as one ring.
_Dimensions._--Diameter of the disk (with five rings) 0.11; breadth of each
ring 0.011; pores 0.004.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
2. _Tripodictya triacantha_, n. sp. (Pl. 42, fig. 7).
All rings of the disk concentric, circular, of the some breadth, connected
by very numerous irregular radial beams, the number of which increases
towards the periphery. Pores irregular, roundish, two on the breadth of
each ring. Three marginal spines spindle-shaped, as long as the radius of
the disk, and in the middle part as broad as one ring.
_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of each
ring 0.012; pores 0.004.
_Habitat._--North Pacific, Station 253, depth 3125 fathoms.
3. _Tripodictya tribelonia_, n. sp. (Pl. 42, fig. 9).
All rings of the disk, or a part of them, not concentric, spirally
convoluted, of equal breadth, connected by numerous irregular, interrupted
radial beams, the number of which increases from the centre. (In one
marginal view of the disk, Pl. 42, fig. 9, the disk seemed to be composed
of seven {506}parallel chambered plates in the central part, and five
similar plates in the peripheral part.) Pores irregular, roundish, three on
the breadth of each ring. Three marginal spines long and thin, cylindrical
(as in _Staurodictya cruciata_, Pl. 42, fig, 4), longer than the diameter
of the disk, and half as thick as one ring.
_Dimensions._--Diameter of the disk (with nine rings) 0.18; breadth of each
ring 0.01; pores 0.002 to 0.004.
_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms.
Genus 220. _Staurodictya_,[259] Haeckel, 1881, Prodromus, p. 460.
_Definition._--#Porodiscida# with four solid radial spines (commonly
crossed at right angles) on the margin of the circular or quadrangular
disk.
The genus _Staurodictya_ is characterised by four marginal spines, lying
opposite in pairs in two crossed equatorial diameters of the disk,
perpendicular one to another. Sometimes the regular rectangular position of
the spines becomes more or less irregular. Commonly the marginal spines are
the extreme prolongations of four internal crossed radial beams, which are
either rectilinear or zigzag-shaped. In the latter case the concentric
disposition of the circular rings becomes more or less spiral. Perhaps
_Staurodictya_ has a near relation to the Stauralastrida (or to the
Euchitonida with four crossed chambered arms--_Stauralastrum_,
_Histiastrum_, &c.).
Subgenus 1. _Staurodictyon_, Haeckel.
_Definition._--All rings of the disk concentric (commonly circular,
sometimes with four incisions, produced by two crossed constrictions, or
nearly square).
1. _Staurodictya medusa_, n. sp. (Pl. 42, fig. 3).
All rings of the disk concentric, of nearly equal breadth, divided into
four quadrants by two perradial constrictions (perpendicular one to
another). Pores irregular, roundish, two to three on the breadth of each
ring. Four marginal spines strong, pyramidal, nearly as long as the radius
of the disk. Margin between them denticulated.
_Dimensions._--Diameter of the disk (with four rings) 0.13; breadth of each
ring 0.015; pores 0.002 to 0.01.
_Habitat._--North Pacific, Station 244, depth 2900 fathoms.
2. _Staurodictya ciliata_, n. sp. (Pl. 42, fig. 2).
All rings of the disk concentric, of nearly equal breadth, circular or
roundish, without perradial constrictions. Pores subregular, circular,
three to four on the breadth of each ring. Four marginal {507}spines short,
pyramidal, about as long as the breadth of one ring. Margin between them
ciliated, with thin radial bristles.
_Dimensions._--Diameter of the disk (with four rings) 0.13; breadth of each
ring 0.015; pores 0.0025.
_Habitat._--South Pacific, Station 295, depth 1500 fathoms.
3. _Staurodictya elegans_, n. sp. (Pl. 42, fig. 1).
All rings of the disk concentric, circular, or roundish, of increasing
breadth towards the margin; the fifth ring twice as broad as the first.
Pores irregular, roundish, two to three on the breadth of each ring. Four
marginal spines very large, conical, with a thin pedicle at the base,
cancellated by ten to twelve deep furrows, about as long as the radius of
the disk and three times as long as broad at the base (above the pedicle).
Margin between them ciliated, with numerous short radial spines.
_Dimensions._--Diameter of the disk (with six rings) 0.14; breadth of the
inner rings 0.006, of the outer 0.012; pores 0.002 to 0.008.
_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.
4. _Staurodictya quadrispina_, Haeckel.
_Stylodictya quadrispina_, Haeckel, 1862, Monogr. d. Radiol., p. 496,
Taf. xxix. fig. 4.
All rings of the disk concentric, circular, of increasing breadth towards
the margin; the fourth ring twice as broad as the second. Pores irregular,
roundish, two to three on the breadth of each ring. Four marginal spines
short and thin, conical, about as long as the breadth of one ring. Margin
between them smooth.
_Dimensions._--Diameter of the disk (with six rings) 0.12; breadth of the
inner rings 0.006, of the outer rings 0.012; pores 0.001 to 0.006.
_Habitat._--Mediterranean, Atlantic (Canary Islands), surface.
Subgenus 2. _Staurospira_, Haeckel.
_Definition._--All rings of the disk or a part of them not concentric,
spirally convoluted; spiral line simple or double, sometimes half or
irregular, interrupted.
5. _Staurodictya cruciata_, n. sp. (Pl. 42, figs. 4, 5).
All rings of the disk nearly of the same breadth, not concentric,
half-spiral, interrupted by four zigzag-shaped radial beams crossed in two
diameters perpendicular one to another. The quarter ring of each quadrant
halving both neighbouring quarters. Pores irregular, roundish, two on the
breadth of each ring. Pores of the outermost (eighth) ring much smaller
than the others. Four marginal spines cylindrical or nearly spindle-shaped,
thick, about as long as the radius of the disk. Margin between them smooth.
_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of each
ring 0.011; pores 0.004.
_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.
{508}6. _Staurodictya splendens_, Haeckel.
_Stylodictya splendens_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xxiii. fig. 9.
All rings of the disk nearly of the same breadth, not concentric,
half-spiral, interrupted by four zigzag-shaped perradial beams, crossed in
two diameters. The quarter ring of each quadrant halving both neighbouring
quarters. Pores regular, circular, only one single on the breadth of each
ring. Four marginal spines conical or spear-shaped, about half as long as
the radius of the disk. Margin between them ciliated, with short
bristle-shaped radial spines.
_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of each
ring 0.012; pores 0.004.
_Habitat._--Fossil in the rocks of Barbados.
7. _Staurodictya grandis_, n. sp.
All rings of the disk (twelve to sixteen) of the same breadth, not
concentric, irregular, partly spiral, interrupted by irregular turnings,
and by ramified radial beams, which divide each ring into numerous square
chambers. Pores subregular, circular, only one single on the breadth of
each ring (and on each chamber). Four marginal spines short and stout,
conical, twice as long as broad at the base, four to five times as long as
the breadth of one ring. Margin between them dentated.
_Dimensions._--Diameter of the disk (with sixteen rings) 0.3; breadth of
each ring 0.01; pores 0.005.
_Habitat._--Pacific, central area, Stations 265 to 268, depth 2900 fathoms;
also fossil in the Tertiary rocks of Barbados.
8. _Staurodictya ocellata_, Haeckel.
_Stylodictya ocellata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xxiii. fig. 7.
All rings of the disk irregular, not concentric, half-spiral, interrupted
by four zigzag-shaped, crossed, radial beams; the quarter ring of each
quadrant halving both neighbouring quarters. Breadth of the rings
increasing towards the periphery; the fourth ring twice as broad as the
second. Pores irregular, with increasing size from the centre, three on the
breadth of each ring. Four marginal spines thick and long, cylindrical;
margin between them smooth.
_Dimensions._--Diameter of the disk (with four rings) 0.1; breadth of the
inner rings 0.01, of the outer 0.02; pores 0.002 to 0.006.
_Habitat._--Fossil in the rocks of Barbados.
_Stylodictya haeckelii_, Zittel, 1876, L. N. 29, p. 85, Taf. ii. fig. 9, is
a fossil Cretaceous species, related to _Stylodictya multispina_.
{509}Genus 221. _Stylodictya_,[260] Ehrenberg, 1847, Monatsber. d. k.
preuss. Akad. d. Wiss. Berlin, p. 54.
_Definition._--#Porodiscida# with numerous (five or more, commonly eight to
twelve) solid radial spines, regularly or irregularly disposed on the
margin of the circular or polygonal disk; margin simple, without a porous
equatorial girdle.
The genus _Stylodictya_ comprises the majority of this subfamily, in which
the number of the marginal spines exceeds four. Commonly we find eight to
twelve spines, more or less regularly disposed (four perradial and four
interradial, or four perradial and eight adradial); but often also the
number and disposition become irregular (sometimes very large). In my
Monograph (1862 pp. 495, 515) I had separated the concentric disks with
closed circular rings (as true _Stylodictya_, s. str.) from the spiral
disks with convoluted rings (_Stylospira_). But I retain these two groups
here only as two subgenera, as intermediate forms between them are very
common, and often a part of the disk concentric, a part spiral (compare
above, p. 492).
Subgenus 1. _Stylodictyon_, Haeckel, 1862, Monogr. d. Radiol., p. 495.
_Definition._--All rings of the disk concentric, commonly circular (rarely
a little elliptical or polygonal).
1. _Stylodictya gracilis_, Ehrenberg.
_Stylodictya gracilis_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 28.
_Stylodictya gracilis_, Ehrenberg, 1873, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 257; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf.
xxiii. fig. 3.
_Stylodictya gracilis_, Haeckel, 1862, Monogr. d. Radiol., p. 499.
All rings of the disk concentric, circular, of equal breadth (the first
ring sometimes, but not constantly, four-lobed). Pores regular, circular,
small, three on the breadth of each ring. Four perradial beams (crossed in
two perpendicular diameters) beginning from the circular central chamber,
four interradial beams from the first or second ring (sometimes others
between them). Beams prolonged into eight to twelve (or more) marginal
spines, bristle-shaped, as long as the radius of the shell.
_Dimensions._--Diameter of the disk (with four rings) 0.12; breadth of each
ring 0.013; pores 0.0025.
_Habitat._--Fossil in Tertiary rocks of Barbados and Nicobar; living in the
depths of the Pacific and Atlantic.
{510}2. _Stylodictya multispina_, Haeckel.
_Stylodictya multispina_, Haeckel, 1862, Monogr. d. Radiol., p. 496, Taf.
xxix. fig. 5.
_Stylodictya forbesii_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 160, Taf. xxiii. fig. 6.
All rings of the disk concentric, circular, of equal breadth. Pores
regular, circular, two and a half to three on the breadth of each ring.
Eight to twelve radial beams beginning from the central chamber, others
from the inner rings. Commonly from the third or fourth ring arise
twenty-four to thirty (sometimes forty or more) piercing beams, which are
prolonged at the margin into bristle-shaped radial spines, as long as the
breadth of two to four rings.
_Dimensions._--Diameter of the disk (with seven rings) 0.2; breadth of each
ring 0.013; pores 0.004.
_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface
and various depths.
3. _Stylodictya hastata_, Ehrenberg.
_Stylodictya hastata_, Ehrenberg, 1873, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 257; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf.
xxiii. fig. 5.
_Stylodictya gracilis_, Bury, 1862, Polycystins of Barbados, pl. ii. fig.
1.
All rings of the disk concentric, circular, of equal breadth. Pores
regular, circular, very small, two on the breadth of each ring. Eight to
twelve marginal spines very large, spear-shaped, sulcated, pyramidal,
nearly as long as the diameter of the disk, with a thin pedicle at the
base, above this as thick as the breadth of one ring.
_Dimensions._--Diameter of the disk (with five rings) 0.13; breadth of each
ring 0.012; pores 0.003.
_Habitat._--Fossil in the rocks of Barbados.
4. _Stylodictya stellata_, Bailey.
_Stylodictya stellata_, Bailey, 1856, Amer. Journ., vol. xxii. p. 6, pl.
i. fig. 20.
_Stylodictya stellata_, Haeckel, 1862, Monogr. d. Radiol., p. 499.
All rings of the disk concentric, circular, of equal breadth. Pores
regular, circular, very small, two on the breadth of each ring. Marginal
spines fourteen (probably variable in number, twelve to sixteen), very
thick and short, conical; their length seems to be equal to their basal
breadth and to the breadth of one ring. Related to _Stylochlamydium_?
_Dimensions._--Diameter of the disk (with five rings) 0.11; breadth of each
ring 0.01; pores 0.003.
_Habitat._--North Pacific, depths of the Kamtschatka Sea, Bailey; Station
241, depth 2300 fathoms.
5. _Stylodictya arachnia_, Haeckel.
_Stylodictya arachnia_, Haeckel, 1862, Monogr. d. Radiol., p. 497.
_Stylocyclia arachnia_, J. Müller, 1856, p. 492; Abhandl. d. k. Akad. d.
Wiss. Berlin, 1858, p. 41, Taf. i. figs. 8, 9.
All rings of the disk concentric, circular, or polygonal; their breadth
increases from the centre towards the periphery, so that the fourth or
fifth ring is twice as broad as the second. Pores {511}subregular,
circular, two on the breadth of each ring. Radial beams partly piercing.
Marginal spines eight to sixteen (commonly twelve), bristle-shaped, very
thin, once to three times as long as the diameter of the disk. (On the
numerous varieties of this common species compare my Monograph, 1862, p.
498.)
_Dimensions._--Diameter of the disk (with ten rings) 0.22; breadth of the
inner rings 0.004 to 0.008, of the outer 0.012 to 0.015; pores 0.003 to
0.005.
_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific,
surface.
6. _Stylodictya solmaris_, n. sp.
All rings of the disk concentric, polygonal, with eight to sixteen rounded
corners; their breadth increases from the centre; eighth ring twice as
broad as the second. Pores subregular circular, large, only one pore on the
breadth of each ring. Twenty to thirty marginal spines, bristle-shaped,
undulating, about as long as (or longer than) the diameter of the disk.
_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of the
inner rings 0.005, of the outer 0.012; pores 0.004 to 0.008.
_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.
7. _Stylodictya octogonia_, n. sp.
All rings of the disk concentric, increasing in breadth from the centre.
The outer rings (five to eight) regular, octogonal, twice as broad as the
circular inner rings. Pores subregular, circular, two to three on the
breadth of each ring. Eight piercing perradial spines (alternating with the
eight corners of the octogonal rings) bristle-shaped, longer than the
diameter of the disk.
_Dimensions._--Diameter of the disk (with eight rings) 0.24; breadth of the
inner rings 0.006, of the outer 0.014; pores 0.005 to 0.01.
_Habitat._--North Atlantic, Station 353, depth 2965 fathoms.
Subgenus 2. _Stylodictula_, Haeckel.
_Definition._--Rings of the disk partly concentric, completely annular;
partly spiral or interrupted, often irregular.
8. _Stylodictya perispira_, n. sp.
Inner rings of the disk (two to four) concentric, circular, or roundish,
outer rings forming a simple spiral, breadth a little increasing from the
centre. Pores subregular, circular, about two on the breadth of each ring.
Marginal spines bristle-shaped, ten to fifteen, about as long as the
diameter of the disk.
_Dimensions._--Diameter of the disk (with eight rings) 0.2; breadth of each
ring 0.013; pores 0.004.
_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.
{512}9. _Stylodictya centrospira_, n. sp. (Pl. 41, fig. 9).
Inner rings of the disk (three or four) convoluted in a simple or double
spiral, often interrupted or irregular; outer rings (two to three)
concentric, circular, or roundish. Breadth of the rings variable,
irregular. Pores irregular, of very different sizes, in the outer
concentric part twice to four times as large as in the inner spiral part.
Radial beams partly interrupted, partly piercing. Marginal spines fifty to
eighty, very variable in size and number, commonly fifteen to twenty strong
conical spines, twice to three times as long as the ring-breadth, and
numerous (thirty to sixty) smaller spines. Very variable.
_Dimensions._--Diameter of the disk (with seven rings) 0.2; breadth of the
rings 0.01 to 0.02; pores 0.002 to 0.01.
_Habitat._--Pacific, central area, Stations 263 to 274, depth 2350 to 2925
fathoms.
10. _Stylodictya setigera_, Ehrenberg.
_Stylodictya setigera_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xxiii. fig. 4.
Inner rings of the disk (two to three) convoluted in a simple or double
spiral, outer rings (two to three) concentric, circular, or roundish.
Breadth of the rings nearly equal. Pores regular, circular, three on the
breadth of each ring. Marginal spines twenty to forty, bristle-shaped,
about twice as long as the ring-breadth. (The specimen figured by Ehrenberg
was a young one; in older specimens I found the inner spiral disk
surrounded by two to three concentric circular rings.)
_Dimensions._--Diameter of the disk (with six rings) 0.16; breadth of the
rings 0.12; pores 0.003.
_Habitat._--Fossil in the rocks of Barbados; also living in the depths of
the Central Pacific, Station 266, depth 2750 fathoms.
Subgenus 3. _Stylospira_, Haeckel, 1862, Monogr. d. Radiol., p. 515.
_Definition._--All rings of the disk convoluted in a simple or double
spiral (sometimes also in quartered half-spirals).
11. _Stylodictya heliospira_, n. sp. (Pl. 41, fig. 8).
_Stylospira heliospira_, Haeckel, 1879, MS.
All rings of the disk convoluted in a simple regular spiral, increasing in
breadth from the centre towards the periphery; the sixth ring twice as
broad as the second. Pores irregular, roundish, two on the breadth of each
ring. Marginal spines numerous, thirty to forty, bristle-shaped, nearly
half as long as the radius of the disk.
_Dimensions._--Diameter of the disk (with seven rings) 0.16; breadth of the
inner rings 0.008, of the outer 0.016; pores 0.002 to 0.006.
_Habitat._--Mediterranean, Portofino near Genoa, surface; also fossil in
the Tertiary rocks of Sicily; Caltanisetta, Haeckel.
{513}12. _Stylodictya hertwigii_, Haeckel.
_Stylospira arachnia_, R. Hertwig, 1879, Organismus d. Radiol., p. 59,
Taf. vi. fig. 8.
All rings of the disk convoluted in a simple regular spiral, with
increasing breadth from the centre; the fifth ring twice as broad as the
second. Pores regular, circular, two on the breadth of each ring. Twelve
piercing radial beams and some others interrupted, prolonged into twelve to
twenty radial marginal spines, bristle-shaped, about as long as the
diameter of the disk.
_Dimensions._--Diameter of the disk (with five rings) 0.15; breadth of the
second ring 0.01, of the fifth 0.02; pores 0.006.
_Habitat._--Mediterranean (Messina), R. Hertwig.
13. _Stylodictya dujardinii_, Haeckel.
_Stylospira dujardinii_, Haeckel, 1862, Monogr. d. Radiol., p. 515, Taf.
xxix. figs. 9, 10.
All rings of the disk convoluted in a simple regular spiral, of nearly
equal breadth. Pores regular, circular, two on the breadth of each ring.
Very numerous (twenty to thirty or more) piercing radial beams, prolonged
into bristle-shaped marginal spines, about as long as the diameter of the
disk.
_Dimensions._--Diameter of the disk (with six rings) 0.12; breadth of each
ring 0.01; pores 0.004.
_Habitat._--Mediterranean (Messina), Haeckel.
14. _Stylodictya echinastrum_, Ehrenberg.
_Stylodictya echinastrum_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xxiii. fig. 1.
All rings of the disk convoluted in a double spiral, of nearly equal
breadth. Pores irregular, roundish, two to three on the breadth of each
ring. Marginal spines numerous, twenty to thirty, of very different size,
the largest conical, strong, about as long as the diameter of the disk, and
on the base as broad as one ring.
_Dimensions._--Diameter of the disk (with five rings) 0.12; breadth of each
ring 0.01; pores 0.002 to 0.006.
_Habitat._--Fossil in the rocks of Barbados.
15. _Stylodictya clavata_, Ehrenberg.
_Stylodictya clavata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 84, Taf. xxiii. fig. 2.
All rings of the disk convoluted in a half spiral, of nearly equal breadth;
each ring by four zigzag beams (crossed in two perpendicular diameters)
divided into four equal quarters; the spiral line of each quarter ring
halving both neighbouring quarters. Pores regular, circular, two on the
breadth of each ring. Eight marginal spines short, conical, with thin
pedicle; four perradial (as {514}prolongations of the four internal beams)
alternating with four interradial spines arising from the margin of the
disk.
_Dimensions._--Diameter of the disk (with five rings) 0.13; breadth of each
ring 0.014; pores 0.003.
_Habitat._--Fossil in the rocks of Barbados.
Genus 222. _Stylochlamydium_,[261] Haeckel, 1881, Prodromus, p. 460.
_Definition._--#Porodiscida# with numerous (five or more, commonly eight to
twelve) solid radial spines, regularly or irregularly disposed on the
margin of the circular or polygonal disk; margin of the disk surrounded by
a thin, porous (but not chambered), equatorial girdle.
The genus _Stylochlamydium_ is intermediate between _Perichlamydium_ (with
which it was formerly united) and _Stylodictya_. It deals with the former
in the peculiar equatorial girdle, with the latter in the radial spines of
the disk margin, which pierce the girdle. To both these genera it shows
slow transitions, and can hardly be subjected to a sharp definition.
Subgenus 1. _Stylochlamys_, Haeckel.
_Definition._--All rings of the disk concentric, circular (or somewhat
polygonal).
1. _Stylochlamydium asteriscus_, n. sp. (Pl. 41, fig. 10).
_Perichlamydium asteriscus_, Haeckel, 1879, MS.
All rings of the disk concentric, circular, or polygonal, with increasing
breadth from the centre; the fifth ring twice as broad as the second. Pores
irregular, roundish, three to four on the breadth of each ring; in the
rings two to six times as large as in the equatorial girdle, which is half
as broad or two-thirds as broad as the radius of the disk. Twelve
bristle-shaped radial spines are connected by the girdle near to the
points; four crossed spines arising from the central chamber; two others
between these in each quadrant arising from the first ring.
_Dimensions._--Diameter of the disk (with five rings) 0.15, with the girdle
0.25; breadth of the second ring 0.01, of the fifth ring 0.02; pores 0.001
to 0.005.
_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.
2. _Stylochlamydium limbatum_, Haeckel.
_Perichlamydium limbatum_, Ehrenberg, 1847, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 20.
_Perichlamydium limbatum_, Haeckel, 1862, Monogr. d. Radiol., p. 494.
All rings of the disk concentric, circular, of equal breadth. Pores
regular, circular, two on the breadth of each ring; twice to three times as
large as the fine pores of the equatorial girdle, which is {515}about half
as broad as the radius of the disk. Twelve (or eleven) bristle-shaped
radial spines are connected by the girdle near to the points, irregularly
disposed.
_Dimensions._--Diameter of the disk (with five rings) 0.12, with the girdle
0.2, breadth of each ring 0.01; pores 0.001 to 0.003.
_Habitat._--Fossil in the Tertiary rocks of Sicily, Caltanisetta, Grotte.
3. _Stylochlamydium venustum_, Haeckel.
_Perichlamydium venustum_, Bailey, 1856, Amer. Journ., vol. xxii. p. 5,
pl. i. figs. 16, 17.
_Perichlamydium venustum_, Haeckel, 1862, Monogr. d. Radiol., p. 495.
All rings of the disk concentric, circular, of equal breadth. Pores
regular, circular, everywhere of nearly equal size, three on the breadth of
each ring, a little smaller in the equatorial girdle, which is about as
broad as the radius of the disk. Twenty to twenty-four bristle-shaped
radial spines, irregularly disposed, proceed with their free points over
the margin.
_Dimensions._--Diameter of the disk (with four rings) 0.1, with the girdle
0.3; breadth of each ring 0.011; pores 0.002.
_Habitat._--North Pacific, Kamtschatka, Bailey.
4. _Stylochlamydium æquale_, Haeckel.
_Perichlamydium æquale_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 109, pl.
v. fig. 2.
All rings of the disk concentric, circular, with increasing breadth from
the centre; the sixth ring twice as broad as the second. Pores regular,
circular, everywhere of equal size; on the breadth of the inner rings one,
of the outer two, of the girdle three pores. Girdle only one-fourth as
broad as the radius of the disk. About twenty bristle-shaped radial spines,
irregularly disposed, are connected by the girdle near to the points.
_Dimensions._--Diameter of the disk (with six rings) 0.11, with the girdle
0.17; breadth of the second ring 0.006, of the sixth 0.013; pores 0.006.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
Subgenus 2. _Stylochlamyum_, Haeckel.
_Definition._--Rings of the disk all (or in part) not concentric, spirally
convoluted or irregular.
5. _Stylochlamydium perispirale_, Haeckel.
_Perichlamydium limbatum_, var. Stöhr, 1880, Palæontogr., vol. xxvi. p.
109, Taf. v. fig. 1.
Inner rings of the disk concentric, circular, outer rings convoluted
spirally, all rings of equal breadth. Pores regular, circular, two on the
breadth of each ring, twice as large as in the equatorial {516}girdle,
which is about half as broad as the radius of the disk. Twelve to sixteen
bristle-shaped radial spines, irregularly disposed, are connected by the
girdle near to the points.
_Dimensions._--Diameter of the disk (with six rings) 0.12, with the girdle
0.2; breadth of each ring 0.011; pores in the central disk 0.004, in the
girdle 0.002.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
6. _Stylochlamydium spongiosum_, Haeckel.
_Perichlamydium spongiosum_, Stöhr, 1880, Palæontogr., vol. xxvi, p. 109,
Taf. v. fig. 3.
Rings of the disk partly concentric, partly spiral, more or less irregular
and often interrupted, with increasing breadth from the centre. Central
part of the disk more or less spongy and obscure. Equatorial girdle half as
broad as the radius of the chambered disk, with smaller pores than the
latter, pierced by twenty to thirty thin, bristle-shaped radial beams,
which proceed over the margin of the disk.
_Dimensions._--Diameter of the disk (with ten rings) 0.2, with the girdle
0.3; breadth of the rings 0.005 to 0.015; pores 0.001 to 0.005.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms; also
fossil in the Tertiary rocks of Barbados and Sicily.
Subfamily 5. EUCHITONIDA, Haeckel.
_Definition._--#Porodiscida# with two or more (commonly three or four)
radial chambered or spongy arms on the margin of the concentrically
annulated disk, situated in its equatorial plane (with or without a
connecting patagium between the arms).
Genus 223. _Amphibrachium_,[262] Haeckel, 1881, Prodromus, p. 460.
_Definition._--#Porodiscida# with two simple, undivided, chambered arms,
opposite in one axis, without a patagium.
The genus _Amphibrachium_ opens the long series of the Euchitonida, or of
those Porodiscida which bear on the margin of the circular central disk a
certain number of chambered arms, composed of a series of chambers which
are separated by transverse septa. The first group or tribe of this
subfamily is formed by the Amphibrachida, in which the disk bears only two
arms opposite on the poles of one axis. The simplest form of these is
_Amphibrachium_, in which both arms are simple, equal, and without a
patagium or spongy connecticulum.
{517}Subgenus 1. _Amphibrachella_, Haeckel.
_Definition._--Both arms equal, of the same form and size, blunt at the
distal end, without a terminal spine.
1. _Amphibrachium sponguroides_, n. sp.
Both opposite arms of the same form and size, nearly cylindrical, three
times as long as broad, with six to eight transverse septa or joints, at
the distal end rounded, blunt, without a terminal spine.
_Dimensions._--Radius of each arm 0.22, breadth 0.065.
_Habitat._--Antarctic Ocean, Station 154, surface.
2. _Amphibrachium lanceolatum_, n. sp.
Both arms equal, lanceolate, in the middle part three times as broad as at
the two ends, two and a half times as long as broad, with eight to nine
transverse septa, at the distal end blunt, without a terminal spine.
_Dimensions._--Radius of each arm 0.3, greatest breadth 0.09.
_Habitat._--Pacific, central area, Station 267, depth 2700 fathoms.
3. _Amphibrachium dilatatum_, n. sp. (Pl. 44, fig. 6).
Both arms equal, trapezoidal, somewhat broader than long, on the convex
distal end three times as broad as on the narrow base, with five to six
transverse septa, without a terminal spine. Central disk large, somewhat
irregular, with three to four rings, twice as broad as the base of the
arms.
_Dimensions._--Radius of each arm 0.32, basal breadth 0.15, terminal
breadth 0.44.
_Habitat._--South Atlantic, off Patagonia, Station 319, surface.
Subgenus 2. _Amphibrachidium_, Haeckel.
_Definition._--Both arms equal, of the same size and form, with terminal
spines.
4. _Amphibrachium amphilonche_, n. sp.
Both arms equal, lanceolate, in the middle part four times as broad as at
the two ends, twice as long as broad; on the distal end of each arm is a
long conical spine.
_Dimensions._--Radius of each arm (without terminal spine) 0.2, breadth
0.08.
_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms.
{518}5. _Amphibrachium capitatum_, n. sp.
Both arms equal, club-shaped, three times as long as broad, in the outer
distal half thickened, three times as broad as at the narrow base; on the
distal end of each arm a strong, angular, terminal spine. (The form of the
arms like that of _Stephanastrum capitatum_, Pl. 44, fig. 1.)
_Dimensions._--Radius of each arm 0.22, basal breadth 0.02, terminal
breadth 0.06.
_Habitat._--Equatorial Atlantic, Station 347, surface.
6. _Amphibrachium armatum_, n. sp.
Both arms equal, four times as long as broad, in the thickened distal part
twice as broad as at the base, thorny, with twenty to thirty larger spines
on the distal end, and a very large pyramidal spine in the longitudinal
axis. (The form of the arms like that of the odd arm in _Euchitonia
carcinus_, Pl. 43, fig. 10.)
_Dimensions._--Radius of each arm 0.24, basal breadth 0.03, distal breadth
0.06.
_Habitat._--North Pacific, Station 244, depth 2900 fathoms.
Subgenus 3. _Amphibrachoma_, Haeckel.
_Definition._--Both arms of different size or form, without terminal
spines.
7. _Amphibrachium indicum_, n. sp.
Both arms club-shaped, but very different in size and form; larger arm
three times as long and twice as broad as the smaller arm; the larger with
nine joints slowly increasing in size, the smaller with four joints,
rapidly increasing; the terminal joint three times as broad as the basal.
Distal end blunt, rounded, without spines.
_Dimensions._--Radius of the larger arm 0.24, of the smaller 0.08; distal
breadth of the former 0.06, of the latter 0.03; basal breadth 0.015.
_Habitat._--Indian Ocean, Ceylon, Haeckel, surface.
Subgenus 4. _Amphibrachura_, Haeckel.
_Definition._--Both arms of different size or form, with terminal spines.
8. _Amphibrachium clavula_, n. sp.
Both arms different in size and form; larger arm club-shaped, four times as
long as broad, at the distal end three times as broad as at the base, and
twice as long as the smaller arm, which resembles a stalked knob, with thin
basal peduncle and spherical distal part. Ends of the two arms {519}thorny
(with numerous smaller, and three to five larger spines); one very large
conical terminal spine on each pole of the main axis.
_Dimensions._--Radius of the larger arm 0.3, of the smaller 0.15; distal
breadth of the former 0.06, of the latter 0.04; basal breath 0.02.
_Habitat._--South Atlantic, Station 333, surface.
Genus 224. _Amphymenium_,[263] Haeckel, 1881, Prodromus, p. 460.
_Definition._--#Porodiscida# with two simple, undivided, chambered arms,
opposite in one axis, connected by a patagium.
The genus _Amphymenium_ differs from the preceding _Amphibrachium_, its
ancestral form, by development of a patagium or connecticulum between both
arms. This forms a latticed or more spongy envelop, which surrounds either
the middle part of the shell, or the whole shell with exception of the
distal ends of both arms. If the envelop become very spongy, the shell may
be confounded with the cylindrical Ellipside _Spongocore_ (nearly allied to
_Spongurus_); possibly also _Ommatogramma_ of Ehrenberg belongs to this
genus.
Subgenus 1. _Ommatogramma_, Ehrenberg (?).
_Definition._--Both opposite arms of the same size and form, blunt, without
terminal spines.
1. _Amphymenium pupula_, n. sp. (Pl. 44, fig. 8).
Both arms equal, twice as long as broad, three-jointed; the terminal joint
egg-shaped, as large as both other joints together; distal end rounded,
blunt. Patagium nearly complete, enveloping the arms with exception of the
distal end. Perimeter nearly spindle-shaped.
_Dimensions._--Radius of each arm 0.17, greatest breadth 0.06; transverse
breadth of the patagium 0.13.
_Habitat._--Pacific, central area, Station 273, depth 2350 fathoms.
2. _Amphymenium naviculare_, Haeckel.
? _Ommatogramma navicularis_, Ehrenberg, 1872, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 317; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf.
vi. fig. 7.
Both arms equal, three times as long as broad, spongy, not jointed; distal
end a little club-shaped, blunt. Patagium nearly complete, enveloping the
arms with exception of the distal end. Perimeter nearly lanceolate. The
imperfect diagnosis and figure of Ehrenberg make it doubtful {520}whether
this species belongs to the Porodiscida (_Amphymenium_) or to the
Spongodiscida (_Spongobrachium_) or perhaps to the Spongurida
(_Spongocore_).
_Dimensions._--Radius of each arm 0.1, greatest breadth 0.03; transverse
breadth of the patagium 0.05.
_Habitat._--North Pacific, Californian Sea, depth 2600 fathoms, Ehrenberg.
3. _Amphymenium zygartus_, n. sp. (Pl. 44, fig. 7).
Both arms equal, four times as long as broad, with seven to eight joints,
slowly decreasing in size towards the blunt end. Patagium incomplete,
protecting only the middle part of the shell on both sides; on each side
two parallel lattice-plates, connected by transverse radial beams,
perpendicular to the surface. Perimeter nearly rectilinear. (Resembles much
certain forms of _Zygartus_, Pl. 40, but is a true Discoid, no Prunoid.)
Compare also Pl. 45, fig. 8.
_Dimensions._--Radius of each arm 0.2, greatest breadth 0.05; transverse
breadth of the patagium 0.11.
_Habitat._--Pacific, central area, Station 271, surface.
4. _Amphymenium monstrosum_, n. sp. (Pl. 44, fig. 11).
Both arms equal, little longer than broad, with six to seven convex joints.
The axis of both arms is not common and straight, as in all other species
of this genus, but broken, therefore the incomplete patagium, which
envelops only two to three joints of the arms, is on one side convex, on
the other side concave; it is formed by a simple lattice-plate, connected
with the arms by numerous radial beams. This anomalous form, seen only
once, may perhaps be a monstrosity of _Euchitonia_.
_Dimensions._--Radius of each arm 0.12, greatest breadth 0.06; transverse
breadth of the patagium 0.13.
_Habitat._--South Pacific, Station 290, surface.
Subgenus 2. _Ommathymenium_, Haeckel.
_Definition._--Both opposite arms of the same size and form, armed at the
distal end with terminal spines.
5. _Amphymenium amphistylium_, n. sp. (Pl. 44, fig. 9).
Both arms equal, three times as long as broad, thickened towards the
truncated distal end, and armed with a strong pyramidal terminal spine.
Each arm with seven joints, separated by convex, transverse septa, and
halved by a radial beam lying in the longitudinal axis. Patagium
incomplete, cylindrical, enveloping only the middle part of the shell.
_Dimensions._--Radius of each arm 0.18, greatest breadth 0.06; transverse
breadth of the patagium 0.08.
_Habitat._--North Atlantic, Station 354, surface.
{521}6. _Amphymenium fusiforme_, n. sp.
Both arms equal, lanceolate, three times as long as broad in the width,
with seven to eight joints. Distal end pointed, armed with a strong conical
terminal spine. Patagium complete, enveloping the whole shell with
exception of the terminal spines. Whole form spindle-shaped.
_Dimensions._--Radius of each arm 0.2, greatest breadth 0.07; transverse
breadth of the patagium 0.15.
_Habitat._--South Atlantic, Station 330, surface.
Genus 225. _Amphirrhopalum_,[264] Haeckel, 1881, Prodromus, p. 460.
_Definition._--#Porodiscida# with two chambered arms, opposite in one axis,
without a patagium; one arm or both forked at the distal end.
The genus _Amphirrhopalum_ differs from _Amphibrachium_, its ancestral
form, by bifurcation of the distal ends of the arms, which may affect
either both arms, or only one of them.
Subgenus 1. _Amphirrhopalium_, Haeckel.
_Definition._--Both opposite arms of similar size and form, with blunt
branches, without terminal spines.
1. _Amphirrhopalum ximorphum_, n. sp.
Both arms equal, in the proximal half simple, in the distal half forked,
with six to seven transverse septa; distal end of each branch blunt,
without terminal spine, somewhat broader than the base of the whole arm.
Axis of the branches concavely curved. (Resembles _Amphicraspedum
maclaganium_, Pl. 45, fig. 11, but wants the patagium.)
_Dimensions._--Radius of the arms 0.18, basal breadth 0.065; terminal
breadth of each branch 0.075.
_Habitat._--North Pacific, off Japan, Station 240, surface.
2. _Amphirrhopalum amphidicranum_, n. sp.
Both arms equal, in the proximal half simple, in the distal half forked,
with irregular septa; distal end of each arm blunt, without a terminal
spine, smaller than the basal breadth of the arm. Axis of the branches
straight. (Resembles _Dicranastrum furcatum_, Pl. 47, fig. 2, but without
lateral arms.)
_Dimensions._--Radius of each arm 0.15, basal breadth 0.03; terminal
breadth of each branch 0.02.
_Habitat._--Pacific, central area, Station 263, depth 2650 fathoms.
{522}Subgenus 2. _Amphirrhopella_, Haeckel.
_Definition._--Both opposite arms of similar size and form, with terminal
spines.
3. _Amphirrhopalum bigeminum_, n. sp.
Both arms equal, in the proximal larger half simple, in the distal smaller
half forked; each branch triangular, with a strong conical terminal spine.
Axis of the branches straight. (Resembles _Dicranastrum cornutum_, Pl. 45,
fig. 2, but without lateral arms.)
_Dimensions._--Radius of the arms (without spines) 0.15, basal breadth
0.03; breadth of the bifurcation 0.08.
_Habitat._--South Pacific, Station 284, surface.
4. _Amphirrhopalum echinatum_, n. sp. (Pl. 45, fig. 10).
Both arms equal, in the proximal smaller half simple, nearly square, in the
distal larger half forked; the branches thorny, armed at the end with
numerous spines, one larger on the terminal pole of the concavely curved
arm-axis.
_Dimensions._--Radius of the arms (without spines) 0.15, basal breadth
0.05; breadth of branches 0.03.
_Habitat._--Pacific, central area, Station 266, depth 2750 fathoms.
Subgenus 3. _Amphirrhopoma_, Haeckel.
_Definition._--Both opposite arms of different size or form, without
terminal spines.
5. _Amphirrhopalum ypsilon_, n. sp.
Both arms very different. Larger arm simple, egg-shaped, twice as long as
broad; smaller arm in the basal half simple, nearly square, in the distal
half forked; both branches egg-shaped, blunt. (Resembles _Amphicraspedum
wyvilleanum_, Pl. 45, fig. 12, but wants the patagium.)
_Dimensions._--Radius of the larger simple arm 0.18, breadth 0.09; radius
of the smaller forked arm 0.15, breadth of its branches 0.05.
_Habitat._--Indian Ocean, Madagascar, Rabbe, surface.
Genus 226. _Amphicraspedum_,[265] Haeckel, 1881, Prodromus, p. 460.
_Definition._--#Porodiscida# with two chambered arms, opposite in one axis,
connected by a lateral patagium; one arm or both forked at the distal end.
The genus _Amphicraspedum_ exhibits the same bifurcation of the arms as
does _Amphirrhopalum_, but differs from this ancestral form in the
development of a patagium, an external connecticulum between the arms,
which envelops the disk totally or partially.
{523}Subgenus 1. _Amphicraspedon_, Haeckel.
_Definition._--Both arms of equal size and form, without terminal spines of
the branches.
1. _Amphicraspedum maclaganium_, n. sp. (Pl. 45, fig. 11).
Both arms equal, in the proximal half simple, in the distal half forked,
with six to seven transverse septa; distal end of each branch rounded,
blunt, somewhat broader than the base of the whole arm. Divergent axes of
both branches concavely curved. Patagium incomplete, with elliptical
perimeter, enveloping only the middle part of the shell. I call this
interesting species in honour of Miss Nellie Maclagan, the learned
translator of several zoological papers from German into English.
_Dimensions._--Radius of each arm 0.25, basal breadth 0.07; distal breadth
of each branch 0.08; equatorial breadth of the patagium 0.25.
_Habitat._--North Atlantic, off Halifax, Station 50, surface.
Subgenus 2. _Amphicraspedina_, Haeckel.
_Definition._--Both arms of different size or form, without terminal spines
on the branches.
2. _Amphicraspedum wyvilleanum_, n. sp. (Pl. 45, fig. 12).
Both arms different. Larger arm simple, egg-shaped, with eleven convex
joints, one and a half times as long as broad; smaller arm in the basal
half simple, triangular, with six cap-like joints, in the distal half
forked; both branches egg-shaped, with five joints and blunt ends. Patagium
nearly complete with four to five concave chamber-rows. Called in honour of
Sir C. Wyville Thomson.
_Dimensions._--Radius of the larger simple arm 0.18, breadth 0.08; radius
of the smaller forked arm 0.16; breadth of the branches 0.05; transverse
breadth of the patagium 0.2.
_Habitat._--South Atlantic, Station 333, surface.
Subgenus 3. _Amphicraspedula_, Haeckel.
_Definition._--Both arms of different size or form, with terminal spines of
the branches.
3. _Amphicraspedum murrayanum_, n. sp. (Pl. 44, fig. 10).
_Amphymenium murrayanum_, Haeckel, 1879, MS. et Atlas (pl. xliv. fig.
10).
Both arms different in size; the larger one and a half times as long and
broad as the smaller. Both arms triangular, forked at the broader distal
end, with two very strong, conical, divergent, {524}straight terminal
spines. Patagium broad, incomplete, with circular perimeter. Called in
honour of my friend Dr. John Murray.
_Dimensions._--Radius of the larger arm (including the spines) 0.24, of the
smaller 0.16; distance of the terminal points of the former 0.18, of the
latter 0.09; diameter of the patagium 0.2.
_Habitat._--North Atlantic, Færöe Channel, Gulf Stream, surface, John
Murray.
Genus 227. _Dictyastrum_,[266] Ehrenberg, 1860, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 830.
_Definition._--#Porodiscida# with three simple, undivided, chambered arms,
without a patagium; triangular shell regular, with three equal arms and
three equal angles.
The genus _Dictyastrum_ is the simplest form of the Trigonastrida, or of
the Porodiscida, in which the margin of the central disk is furnished with
three chambered arms. In _Dictyastrum_ these are quite simple and regular,
without a patagium, separated by equal angles, so that the whole shell
represents a regular, equilateral triangle, if we connect the distal points
of the arms by lines. The genus _Dictyastrum_, founded by Ehrenberg in
1860, differs from his _Rhopalodictyum_--after his own diagnosis--only by
an insignificant difference in the form of the simple arms, which is
scarcely a specific character. I therefore apply this name here in the
above amended sense, seeing that the only figured species of Ehrenberg
(_Dictyastrum angulatum_) occurs in two different, but externally very
similar forms: one of these is a true Porodiscid (_Dictyastrum_) with two
porous covering-plates and concentric rings; the other is a true
Spongodiscid (_Rhopalodictyum_) with quite spongy, irregular network, and
is probably identical with the _Rhopalodictyum truncatum_ of Ehrenberg.
Subgenus 1. _Dictyastrella_, Haeckel.
_Definition._--Arms with blunt ends, without terminal spines.
1. _Dictyastrum angulatum_, Ehrenberg.
_Dictyastrum angulatum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 289, Taf. viii. fig. 18.
Arms nearly square with straight edges, towards the truncated end a little
broader, about the same diameter as the triangular central disk. The figure
of Ehrenberg seems to represent a Spongodiscid (_Rhopalodictyum
angulatum_), but in the same locality (Philippine Sea) occurs also a true
_Dictyastrum_ of quite the same form, but with three to four concentric
rings of the central disk, and with jointed arms.
{525}_Dimensions._--Radius of each arm (length from the centre to the
distal end) 0.13; breadth of the truncated end 0.1.
_Habitat._--Tropical Pacific, Philippine Sea, Station 200, depth 250
fathoms.
2. _Dictyastrum bandaicum_, Haeckel.
_Rhopalastrum bandaicum_, Harting, 1863, Mikr. Fauna Banda-Zee, p. 16,
Taf. iii. fig. 45.
Arms nearly square, with convex edges, in the middle a little broader than
at both ends, about half the diameter of the central disk. Differs from the
nearly allied preceding species by the half size of the arms and the convex
edges.
_Dimensions._--Radius of each arm 0.12, its greatest breadth 0.07.
_Habitat._--Tropical Pacific, Banda Sea, Harting.
3. _Dictyastrum hexagonum_, n. sp. (Pl. 43, fig. 7).
_Rhopalastrum hexagonum_, Haeckel, 1880, Atlas (pl. xliii. fig. 1).
Arms nearly triangular, one and a third times as broad at the distal end as
long, and three times as broad as at the base. Central disk about the same
diameter. In each arm six simple broad chambers. If we connect the six
corners of the truncated distal ends by straight lines, we get a regular
hexagon.
_Dimensions._--Radius of each arm 0.17, basal breadth 0.06, terminal
breadth 0.17.
_Habitat._--Equatorial Atlantic, Station 347, surface.
4. _Dictyastrum trirrhopalum_, n. sp.
Arms club-shaped, five times as long as broad at the base, at the thickened
end three times as broad as at the base. Diameter of the central disk
equals half the length of the arms. (Similar to _Rhopalastrum malleus_, Pl.
43, fig. 1, but with three equal angles and much smaller disk.)
_Dimensions._--Radius of each arm 0.25, basal breadth 0.04, distal breadth
0.12.
_Habitat._--Pacific, central area, Station 273, surface.
Subgenus 2. _Dictyastromma_, Haeckel.
_Definition._--Arms on the distal end provided with terminal spines.
5. _Dictyastrum trispinosum_, n. sp. (Pl. 43, fig. 5).
_Rhopalastrum trispinosum_, Haeckel, 1881, Prodromus et Atlas (pl. xliii.
fig. 5).
Arms trapezoid, at the rounded distal end twice as broad as at the base,
with a strong and short, conical, terminal spine. Diameter of the circular
central disk about equal to the length and the greatest breadth of the
arms.
_Dimensions._--Radius of each arm 0.15, basal breadth 0.06, distal breadth
0.11.
_Habitat._--Equatorial Atlantic, Station 347, surface.
{526}6. _Dictyastrum triactis_, Ehrenberg.
_Dictyastrum triactis_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 306.
Arms rectilinear, four times as long as broad, with parallel edges, pointed
at the distal end, with a short terminal spine. Diameter of the circular
central disk equal to double the breadth of the arms.
_Dimensions._--Radius of each arm 0.2, breadth 0.04.
_Habitat._--Pacific, Philippine Sea, Station 206, depth 2100 fathoms.
7. _Dictyastrum aculeatum_, n. sp.
Arms lanceolate, three times as long as broad, twice as broad in the middle
as at either end, with thorny surface and numerous conical terminal spines,
one very large in the radius. Central disk triangular, about as broad as
the arms. (Resembles _Rhopalastrum arcticum_, Pl. 43, fig. 6, but differs
by the equal angles and the triangular disk.)
_Dimensions._--Radius of each arm 0.2, breadth 0.06.
_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.
Genus 228. _Rhopalastrum_,[267] Ehrenberg, 1847, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 54.
_Definition._--#Porodiscida# with three simple undivided, chambered arms,
without a patagium; triangular shell bilateral, one odd arm opposite to the
odd angle between two paired arms.
The genus _Rhopalastrum_, founded by Ehrenberg (1847) with a very
insufficient diagnosis, is here retained for those Trigonastrida that agree
in the generic characters with the only species figured by him, viz.,
_Rhopalastrum lagenosum_ (compare my Monograph, 1862, p. 500). It
comprises, therefore, such Euchitonida as agree with the preceding
_Dictyastrum_ in the simple form of the three arms and the absence of a
patagium, but differ from it in the different size of the three angles, and
often also in the divergent form and size of the three arms; one odd arm is
opposite to the odd angle between the two paired arms.
Subgenus 1. _Rhopalastrella_, Haeckel.
_Definition._--Arms with blunt ends, without terminal spines.
1. _Rhopalastrum truncatum_, Haeckel.
_Rhopalastrum truncatum_, Haeckel, 1862, Monogr. d. Radiol., p. 500, Taf.
xxix. fig. 6.
Distance of both paired arms about half as large as their distance from the
odd arm. All three arms nearly of the same form and size, very short and
broad; their breadth nearly equals that of {527}the roundish central disk,
whilst their length reaches only one-fourth of it. End of the arms convex
rounded, without spines.
_Dimensions._--Radius of each arm 0.1, breadth 0.15.
_Habitat._--Mediterranean (Messina), Atlantic (Canary Islands), surface,
Haeckel.
2. _Rhopalastrum pistillum_, Stöhr.
_Rhopalastrum pistillum_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 110,
Taf. v. fig. 4.
Distance between the paired arms about two-thirds as large as their
distance from the odd arm. All three arms nearly of the same form and size,
about three times as long as the diameter of the central disk, at the base
one-third as broad as at the convex rounded end, without spines. Stöhr has
only observed a fragment with one arm; some perfect specimens, which I
found in the Caltanisetta-rock, exhibited nearly the same form as
_Rhopalastrum malleus_ (Pl. 43, fig. 1), but differ from this by the
smaller disk, the broader arms, and the smaller angle between the paired
arms.
_Dimensions._--Radius of all three arms 0.2; basal breadth of each arm
0.045, terminal breadth 0.13.
_Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stöhr),
Caltanisetta (Haeckel).
3. _Rhopalastrum malleus_, n. sp. (Pl. 43, fig. 1).
Distance between the paired arms one and a third times as large as their
distance from the odd arm. All three arms nearly of the same form and size,
hammer-shaped, three times as broad at the truncated distal end as at the
base. Central disk broader than the arms.
_Dimensions._--Radius of each arm 0.25, basal breadth 0.05, distal breadth
0.15.
_Habitat._--South Atlantic, Station 325, surface.
4. _Rhopalastrum lagenosum_, Ehrenberg.
_Rhopalastrum lagenosum_, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 43; Mikrogeol., 1854, Taf. xxii. fig. 22.
_Rhopalastrum lagenosum_, Haeckel, 1862, Monogr. d. Radiol., p. 501.
_Flustrella bilobata_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 81.
_Haliomma lagena_, Ehrenberg, 1840, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 200.
Distance between the paired arms one and a half times as great as their
distance from the odd arm. All three arms nearly of the same form and size,
about one and a half times as long as the diameter of the central disk, at
the base half as broad as at the convex rounded end, without spines.
Ehrenberg has only observed a fragment with two paired arms; some perfect
specimens with three arms, observed by me, differed from the nearly allied
_Rhopalastrum pistillum_ (from the same locality) by the larger disk, the
broader arms, and the larger unpaired angle.
_Dimensions._--Radius of all three arms 0.2, basal breadth 0.05, terminal
breadth 0.09.
_Habitat._--Fossil in Tertiary rocks of Sicily, Caltanisetta.
{528}5. _Rhopalastrum ypsilinum_, n. sp. (Pl. 43, fig. 2).
Distance between the paired arms half as large as their distance from the
odd arm. All three arms at the concavely curved distal end three times as
broad as at the narrow base. Odd arm twice as long and broad as the paired
arms. Central disk smaller than the latter. No terminal spines.
_Dimensions._--Radius of the odd arm 0.32, of the paired arms 0.2; terminal
breadth of the former 0.2, of the latter 0.12.
_Habitat._--Indian Ocean, Cocos Islands, Rabbe, surface.
6. _Rhopalastrum clavatum_, n. sp.
Distance between the paired arms half as large as their distance from the
odd arm. All three arms club-shaped, at the thickened, nearly spherical,
distal end three times as broad as at the narrow base. Odd arm nearly twice
as long and broad as the paired arms. Central disk equal to the distal knob
of the latter. No terminal spines.
_Dimensions._--Radius of the odd arm 0.3, of the paired arms 0.18; distal
breadth of the former 0.16, of the latter 0.08.
_Habitat._--South Atlantic, Station 332, surface.
7. _Rhopalastrum irregulare_, n. sp. (Pl. 43, fig. 8).
Distance between all three arm-points different. All three arms
cylindrical, nearly of the same length, but of different form, irregularly
curved, about four times as long as broad, with blunt ends.
_Dimensions._--Length of each arm about 0.2, breadth 0.05.
_Habitat._--Antarctic Sea, Station 157, depth 1950 fathoms.
Subgenus 2. _Rhopalastromma_, Haeckel.
_Definition._--Arms on the distal end provided with one or more terminal
spines.
8. _Rhopalastrum martellum_, n. sp.
Distance between all three arm-points nearly the same; but the odd arm is
one and a half times as large as both paired arms, and is perpendicular to
the common axis of the latter, therefore the shell has the form of a
hammer. Each arm is twice as broad at the distal end as at the base, and
armed with a conical terminal spine; the latter is vertical in the odd arm,
horizontal in the paired arms.
_Dimensions._--Radius of the odd arm 0.3, of the paired arms 0.15; distal
breadth of the former 0.12, of the latter 0.06.
_Habitat._--North Atlantic, Station 354, surface.
{529}9. _Rhopalastrum triceros_, n. sp. (Pl. 43, fig. 4).
Distance between the paired arms about two-thirds as large as their
distance from the odd arm. All three arms club-shaped, three times as broad
at the thickened distal part as at the base, and armed with one single,
conical, terminal spine. Odd arm of the same breadth, but twice as long as
the paired arms.
_Dimensions._--Radius of the odd arm 0.35, of the paired arms 0.2; basal
breadth 0.04, distal breadth 0.12.
_Habitat._--Pacific, central area, Station 274, surface.
10. _Rhopalastrum hexaceros_, n. sp. (Pl. 43, fig. 3).
Distance between the paired arms equals four-fifths of their distance from
the odd arm. All three arms nearly of the same size, about square, a little
broader at the truncated distal end, which is armed at both corners with a
strong, conical, radial spine.
_Dimensions._--Radius of each arm 0.2, basal breadth 0.1, distal breadth
0.12.
_Habitat._--Indian Ocean, Ceylon, Belligemma, Haeckel, surface.
11. _Rhopalastrum arcticum_, n. sp. (Pl. 43, fig. 6).
Distance between the paired arms half as large as their distance from the
odd arm, which is a little larger. All three arms of the same form,
lanceolate, twice to three times as long as broad, twice as broad in the
middle as at either end. Each arm with twelve to fourteen transverse septa,
at the distal end with a bunch of conical spines, and one single, very
large, pyramidal, terminal spine.
_Dimensions._--Radius of each arm (without spine) 0.17, greatest breadth of
it 0.05 to 0.06.
_Habitat._--Arctic Ocean, lat. 83° 19' N., North Polar expedition of the
"Alert."
Genus 229. _Hymeniastrum_,[268] Ehrenberg, 1847, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 54.
_Definition._--#Porodiscida# with three simple, undivided, chambered arms,
connected by a patagium; triangular shell regular, with three equal arms
and three equal angles.
The genus _Hymeniastrum_ was founded by Ehrenberg (1847) with a very
incomplete diagnosis, and hitherto known only by one single species,
figured by him as _Hymeniastrum pythagoræ_ (Mikrogeol., 1854, Taf. xxxvi.
fig. 31). This form occurs in two different states, externally quite
identical; in one state the central disk (as figured, _loc. cit._), is a
simple lens or hollow disk, containing a medullary shell or "central
chamber"; in the other state the central disk is composed of two concentric
rings surrounding the "central chamber." We retain here the name
_Hymeniastrum_ for this latter state, {530}expressed in the diagnosis given
above, and call the former state (the Coccodiscid) _Hymenactura_ (compare
above, p. 473). One practical advantage, obtained in this way, is that all
genera of #Discoidea# ending with "_-astrum_" belong to the Porodiscida.
_Hymeniastrum_ differs from _Dictyastrum_ by the possession of a patagium,
and from _Euchitonia_ by the equal size of the angles and the arms.
Subgenus 1. _Hymenastrella_, Haeckel.
_Definition._--Arms with blunt ends, without terminal spines.
1. _Hymeniastrum leydigii_, Haeckel.
_Euchitonia leydigii_, Haeckel, 1862, Monogr. d. Radiol., p. 510, Taf.
xxxi. figs. 4, 5.
_Hymeniastrum leydigii_, Haeckel, 1881, Prodromus, p. 460.
_Histiastrum trinacrium_, Haeckel, 1860, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 843.
Arms twice as long as broad, two-thirds as broad at the base as at the
blunt, nearly truncated distal end. Patagium nearly complete, perfectly
filling out the interbrachial spaces, with six to seven regular, concave
chamber-rows; only the truncate terminal faces of the arms free.
_Dimensions._--Radius of the arms 0.15 to 0.18, breadth on their base 0.04
to 0.05, on their broadest distal end 0.06 to 0.07.
_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. Very
common and variable.
2. _Hymeniastrum köllikeri_, Haeckel.
_Euchitonia köllikeri_, Haeckel, 1862, Monogr. d. Radiol., p. 511, Taf.
xxxi. figs. 6, 7.
_Hymeniastrum köllikeri_, Haeckel, 1881, Prodromus, p. 460.
Arms nearly lanceolate, twice as long as broad, half as broad at the base
as at the broadest middle part, pointed at the distal end. Patagium
complete, enveloping the whole triangular disk, with irregular
chamber-rows.
_Dimensions._--Radius of the arms 0.2, breadth on their base 0.04, on the
broadest part 0.08.
_Habitat._--Mediterranean (Messina), surface.
3. _Hymeniastrum gümbelii_, Haeckel.
_Stylactis gümbelii_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 112, Taf.
vi. fig. 1.
Arms twice as long as broad, nearly twice as broad in the circular distal
half as in the square proximal half. Patagium incomplete, circular, with
eight to nine convex chamber-rows, enveloping only the proximal square
halves of the arms; the lenticular distal halves remain free.
_Dimensions._--Radius of the arms 0.14; breadth at the base 0.04, at the
distal lenticular part 0.07.
_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.
{531}4. _Hymeniastrum euclidis_, n. sp. (Pl. 43, fig. 13).
_Euchitonia euclidis_, Haeckel, 1881, Prodromus, p. 460 et Atlas (pl.
xliii. fig. 13).
Arms one and a half times as long as broad, club-shaped, three times as
broad in the oval distal part as in the narrow square proximal part.
Patagium complete, enveloping the whole triangular disk, and also the
convex ends of the arms, with eight to nine convex chamber-rows.
_Dimensions._--Radius of the arms 0.18; breadth at the base 0.025, at the
broadest distal part 0.07.
_Habitat._--Pacific, central area, Stations 270 to 274, surface.
5. _Hymeniastrum pythagoræ_, Ehrenberg.
_Hymeniastrum pythagoræ_, Ehrenberg, 1854 (_partim_), Mikrogeol., Taf.
xxxvi. fig. 31.
Arms nearly as broad as long, two-thirds as broad at the base as at the
truncated distal end. Patagium incomplete, enveloping only the basal half
of the arms, with four to five rectilinear parallel chamber-rows. (This
form has the greatest resemblance to the figure given by Ehrenberg, _loc.
cit._, but differs by the central disk, which is composed of two concentric
rings surrounding the small central chamber; compare above _Hymenactura
pythagoræ_, p. 474.)
_Dimensions._--Radius of the arms 0.18; breadth at the base 0.08, at the
truncated end 0.12.
_Habitat._--Equatorial Atlantic, Station 347, depth 2250 fathoms.
6. _Hymeniastrum archimedis_, n. sp.
Arms nearly triangular, at the truncated, slightly convex end three times
as broad as at the narrow base and one and a third times as broad as long;
each arm with six simple chambers. Patagium incomplete, enveloping only the
basal half of the arms with three to four convex chamber-rows. (Differs
from _Rhopalastrum hexagonum_, Pl. 43, fig. 7, only by the patagium.)
_Dimensions._--Radius of the arms 0.2; breadth at the base 0.07, at the
truncated end 0.2.
_Habitat._--Pacific, central area, Station 274, surface.
Subgenus 2. _Hymenastromma_, Haeckel.
_Definition._--Arms at the distal end provided with radial spines.
7. _Hymeniastrum ternarium_, Haeckel.
_Histiastrum ternarium_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 76, Taf. xxiv. fig. 2.
Arms two and a half times as long as broad, three times as broad at the
truncated end as at the narrow base, with a strong, conical, radial spine
at the end. Patagium incomplete, enveloping only the basal half of the
arms, with three to four convex chamber-rows.
_Dimensions._--Radius of the arms (without terminal spine) 0.02; breadth at
the base 0.025, at the broadest terminal part 0.08.
_Habitat._--Fossil in the rocks of Barbados.
{532}8. _Hymeniastrum trigonarium_, n. sp.
Arms one and a half times as long as broad, a little broader at the rounded
end than at the base, with three strong conical radial spines, one larger
(in the radius of each arm) and two smaller on both sides of this. Patagium
complete, with four to five rectilinear parallel chamber-rows, enveloping
the whole arms (with exception of the terminal spines) and forming a
perfect equilateral triangle.
_Dimensions._--Radius of the arms (without terminal spines) 0.18; breadth
at the base 0.1, at the distal part 0.12.
_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.
Genus 230. _Euchitonia_,[269] Ehrenberg, 1860, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 831 (_sensu emendato_).
_Definition._--#Porodiscida# with three simple, undivided, chambered arms,
connected by a patagium; triangular shell bilateral, one odd arm opposite
to the odd angle between the two paired arms.