Chapter XI: Literature and History (26)

_Definition._--#Pylodiscida# with _Triopyle_-shaped medullary shell and _Pylodiscus_-shaped cortical shell, which is surrounded by an equatorial chambered girdle. No peculiar osculum on the margin of the disk.

The genus _Discozonium_ and the following _Discopyle_ make up together the small group of the Discopylida, or those Pylodiscida in which a discoidal shell like _Pylodiscus_ is surrounded by a marginal equatorial girdle; this girdle is divided into twelve to twenty-four or more chambers by radial beams, which are the external prolongations of the radial marginal spines of _Pylodiscus_. The latter genus bears therefore to _Discozonium_ the same relation as _Sethodiscus_ in the other #Discoidea# does to _Lithocyclia_, or _Phacodiscus_ to _Coccodiscus_.

1. _Discozonium cyclonium_, n. sp.

Disk circular, lenticular, with smooth margin, three times as broad as the triangular, _Triopyle_-shaped medullary shell. Three gates of the cortical shell kidney-shaped, twice as broad as the three {572}arms. Chambered equatorial girdle with twenty to twenty-four subregular chambers (similar to _Discopyle osculata_, Pl. 48, fig. 19, but without any marginal osculum).

_Dimensions._--Diameter of the disk 0.2, of the cortical shell 0.14, of the medullary shell 0.07.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

2. _Discozonium trigonium_, n. sp.

Disk triangular, with thorny margin, four times as broad as the triangular, _Triopyle_-shaped medullary shell. Three gates of the cortical shell egg-shaped, scarcely as broad as the three arms. Chambered equatorial girdle with twenty-four to thirty irregular chambers.

_Dimensions._--Diameter of the disk 0.24, of the cortical shell 0.2, of the medullary shell 0.06.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.

3. _Discozonium hexagonium_, n. sp. (Pl. 48, fig. 18).

Disk hexagonal, with spiny margin, four times as broad as the triangular, _Triopyle_-shaped medullary shell. Three gates of the cortical shell kidney-shaped, one and a half times as broad as the arms. Chambered equatorial girdle with twelve large regular chambers; the radial beams between them are prolonged into twelve strong pyramidal marginal spines (three perradial on the ends of the arms, three interradial on the radii of the gates, six adradial between the former and latter).

_Dimensions._--Diameter of the disk 0.2, of the cortical shell 0.12, of the medullary shell 0.05.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.

Genus 252. _Discopyle_,[291] n. gen.

_Definition._--#Pylodiscida# with _Triopyle_-shaped medullary shell and _Pylodiscus_-shaped cortical shell, which is surrounded by an equatorial chambered girdle. One peculiar osculum, surrounded by a corona of spines, on the margin of the disk.

The genus _Discopyle_ differs from the preceding genus _Discozonium_ in the development of a peculiar marginal osculum, and bears therefore to it the same relation as, in the Porodiscida, _Ommatodiscus_ does to _Porodiscus_ (compare above, p. 500). This peculiar osculum is here also surrounded by a corona of spines, and serves probably for the exit or outlet of a bunch of pseudopodia or a "sarcode-flagellum." Only two species of _Discopyle_ have been observed, which represent perhaps better two different genera; in one species the disk is circular, in the other elliptical. In this latter the osculum lies on one pole of the main axis.

{573}1. _Discopyle osculata_, n. sp. (Pl. 48, fig. 19).

Disk circular with spiny margin, three times as broad as the triangular, _Triopyle_-shaped medullary shell. Three gates of the cortical shell kidney-shaped, on the inside with an interradial spine, twice as broad as the three pentagonal arms. Chambered equatorial girdle with twenty-four subregular chambers, in the radius of one odd gate with a large marginal osculum, which is as broad as the medullary shell, and surrounded by a dense corona of twenty to thirty strong conical spines.

_Dimensions._--Diameter of the disk 0.15, of the cortical shell 0.1, of the medullary shell 0.05, of the marginal osculum 0.06.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.

2. _Discopyle elliptica_, n. sp. (Pl. 48, fig. 20).

Disk elliptical, four-fifths as broad as long, with spiny margin, three times as broad as the triangular, _Triopyle_-shaped medullary shell. Three gates of the cortical shell roundish, on the inside with an interradial spine, little broader than the quadrangular arms. Chambered equatorial girdle with twenty to thirty irregular chambers, on one pole of the main axis with a large marginal osculum, which is one-third as broad as the length of the main axis, and armed with a corona of twenty to thirty short conical spines. The osculum does not correspond to a certain radius.

_Dimensions._--Diameter of the disk 0.15, of the cortical shell 0.08, of the medullary shell 0.04, of the marginal osculum 0.05.

_Habitat._--Central Pacific, Station 267, depth 2700 fathoms.

Family XXIII. #SPONGODISCIDA#, Haeckel (Pl. 41, fig. 11).

_Spongodiscida et Spongocyclida_, Haeckel, 1862, Monogr. d. Radiol.,
pp. 452, 460, 469.
_Spongodiscida_, Haeckel, 1881, Prodromus, p. 461.
_Calodictya_, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss.
Berlin, p. 53 (_partim_).

_Definition._--#Discoidea# without a phacoid shell, with a flat discoidal shell, in which a simple spherical central chamber is surrounded by an irregular spongy framework (sometimes with concentric rings around the central chamber). Surface of the disk quite spongy, without porous sieve-plates.

The family #Spongodiscida# is the sixth and last family of the #Discoidea#, and bears to the other families of this group the same relation as the family Spongosphærida does to the other #Sphæroidea#, or the Spongurida to the other #Prunoidea#. Its characteristic structure consists in the irregular spongy framework of the disk, and mainly in the rough, irregular shape of its spongy surface, which is never covered with porous plates (neither phacoid shell nor corresponding sieve-plates), as in all other #Discoidea#. Of course a little spongy structure occurs also in many Porodiscida {574}and even in some Coccodiscida (principally in the peripheral part of the disk or its chambered arms); but both flat (or convex) surfaces of the disk (at least in the central part) remain here constantly as simple lattice-plates, whilst in all Spongodiscida the whole surface of the disk is spongy.

When I constituted the family Spongodiscida in my Monograph (1862, pp. 452, 460) I had separated from them the Spongocyclida, exhibiting in the central part of the disk a more or less distinct concentric arrangement of the spongy chambers, whilst in the former the delicate spongy framework is quite irregular, composed of branched siliceous threads, connected and interwoven in all directions. But in all Spongocyclida the whole surface of the spongy disk is quite as irregularly rough and deprived of smooth sieve-plates as in all true Spongodiscida, and the more or less concentric structure of the central part of the disk in the former (very variable and often scarcely able to be recognised) seems not sufficient to separate both groups; even the single genera cannot be sufficiently separated by this character. I now therefore give up entirely the group of Spongocyclida (as already done in my Prodromus, 1881). Nevertheless the concentric annular structure in the dark central part of some Spongodiscida is very interesting as transition to the Porodiscida; it indicates already that the former are derived from the latter. Even the single genera in both families are corresponding.

In the new system of "Polycystina," which Ehrenberg gave, 1875 (Abhandl. d. k. Akad. d. Wiss. Berlin, p. 157), are enumerated under the _Calodictya_ four genera "with spongy disk," viz., _Spongodiscus_, _Rhopalodictyum_, _Dictyocoryne_, _Spongaster_. Indeed these four genera, which I here retain, are true Spongodiscida, and must be separated from the other _Calodictya_, the greater part of which are Porodiscida. The number of species of true Spongodiscida now amounts to sixty-seven, which I dispose in thirteen genera.

The whole family may be divided into three subfamilies. The first of these are the Spongophacida (corresponding to the Trematodiscida among the Porodiscida), in which the circular margin of the spongy disk bears no radial appendages; either the margin is quite simple, spongy (_Spongodiscus_), or surrounded by a hyaline, solid, or porous equatorial girdle (_Spongophacus_). The disk is either more lenticular (biconvex) or more flat discoidal (a shortened cylinder), rarely a little biconcave (thicker at the margin than in the centre). The spongy framework of the solid disk is either quite irregular (_Spongodisculus_), or in the central part with concentric circular rings (_Spongocyclia_), or in the central part spirally convoluted (_Spongospira_).

The second subfamily, Spongotrochida, corresponds to the Stylodictyida (among the #Porodiscida#), and is distinguished by solid radial spines on the margin of the disk, disposed in the equatorial plane either irregularly or regularly (after the same order as in the other families of #Discoidea#).

The third subfamily, Spongobrachida, correspond perfectly to the Euchitonida {575}(among the Porodiscida), bearing on the disk-margin two, three, or four spongy arms, commonly disposed regularly in the equatorial plane. Here also occurs the peculiar formation of a "patagium," or of an interbrachial spongy framework different from that of the arms, which connects the arms like a web-membrane in the equatorial plane.

The spongy framework exhibits in all these Spongodiscida no remarkable differences, being everywhere composed of fine branched solid siliceous threads, interwoven in all directions, with irregular meshes of very different size.

The central capsule of all Spongodiscida is filled up with the same spongy framework which covers also both its sides. It grows according to the enveloping skeleton, but remains constantly smaller. The form of the central capsule is circular (lenticular or discoidal) in the Spongophacida and Spongotrochida, whilst in the Spongobrachida it enters into the radial spongy arms, developed from the margin of the spongy disk.

_Synopsis of the Genera of the Spongodiscida._

{Spongy disk with simple
I. Subfamily { margin (without peculiar
Spongophacida. { equatorialgirdle), 253. _Spongodiscus_.
Spongy disk {
without radial {Spongy disk with a peculiar
appendages. { (solid or porous) equatorial
{ girdle, 254. _Spongophacus_.

{ {Two opposite
{ { spines, 255. _Spongolonche_.
II. Subfamily {Few (two, {
Spongotrochida. { three, or {Three marginal
Spongy disk with { four) radial { spines, 256. _Spongotripus_.
solid radial { spines {
spines on the { regularly {Four crossed
margin (in the { disposed. { spines, 257. _Spongostaurus_.
equatorial {
plane). { {Spines only
{Numerous (five { on the
{ to ten or { margin
{ more) radial { (equatorial), 258. _Stylotrochus_.
{ spines, {
{ often {Spines on both
{ irregularly { sides of the
{ disposed. { disk, 259. _Spongotrochus_.

{ {Without a
{Two arms, { patagium, 260. _Spongolena_.
{ opposite in {
{ one axis. {With a
{ { patagium, 261. _Spongobrachium_.
III. Subfamily {
Spongobrachida. { {Without
Spongy disk with { { a patagium, 262. _Rhopalodictyum_.
spongy radial {Three arms on {
arms on the { the margin. {With a
margin (in the { { patagium, 263. _Dictyocoryne_.
equatorial {
plane). { {Without
{ { a patagium, 264. _Spongasteriscus_.
{Four arms in {
{ cross form. {With a
{ { patagium, 265. _Spongaster_.

Subfamily 1. SPONGOPHACIDA, Haeckel, 1881, Prodromus, p. 461.

_Definition._--#Spongodiscida# with a simple circular disk, without radial appendages on the margin (neither solid spines nor chambered arms).

{576}Genus 253. _Spongodiscus_,[292] Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 237.

_Definition._--#Spongodiscida# with a simple circular disk, without radial appendages and without an equatorial girdle on the margin.

The genus _Spongodiscus_ represents the most simple and primitive form of the Spongodiscida, or of those #Discoidea# in which the central disk is more or less spongy, composed of an irregular fine framework. In my Monograph (1862, pp. 452, 460, 469) I had separated the true _Spongodiscus_ (first described by Ehrenberg, _loc. cit._) and the _Spongocyclia_; the former being characterised by the irregular spongy framework of the whole disk, whilst in the latter this framework includes in the central part some concentric circular rings (approaching _Porodiscus_). In the same way afterwards Stöhr (1880, _loc. cit._) separated the genus _Spongospira_ as spongy disks, which include in the central part some spiral convolutions. But as these differences are rather inconstant and not sharply discernible, I think it now better to regard these three forms as subgenera of _Spongodiscus_. All three have the common simple circular disk, without any marginal appendages.

Subgenus 1. _Spongodisculus_, Haeckel.

_Definition._--Spongy framework of the disk quite irregular, without concentric rings or spiral convolutions.

1. _Spongodiscus mediterraneus_, Haeckel.

_Spongodiscus mediterraneus_, Haeckel, 1862, Monogr. d. Radiol., p. 461,
Taf. xii. figs. 14, 15.

Spongy disk plain on both sides, with quite an irregular framework, without concentric rings and without radial piercing beams. Texture everywhere uniform; meshes eight to ten times as broad as the bars.

_Dimensions._--Diameter of the disk 0.08 to 0.24, of the meshes 0.005 to 0.008.

_Habitat._--Mediterranean (Messina), Haeckel; also fossil in the Tertiary rocks of Sicily (Grotte), Stöhr.

2. _Spongodiscus radiatus_, n. sp.

Spongy disk plain on both sides, with quite irregular framework, without concentric rings, but with numerous piercing radial beams which are not prolonged into marginal spines. Texture everywhere uniform; meshes once and a half to twice as broad as the bars.

_Dimensions._--Diameter of the disk 0.12 to 0.15, of the meshes 0.002 to 0.003.

_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.

{577}3. _Spongodiscus resurgens_, Ehrenberg.

_Spongodiscus resurgens_, Ehrenberg, 1854, Mikrogeol., Taf. xxxvB. B.
iv., fig. 16.

_Spongodiscus resurgens_, Stöhr, 1880, Palæontogr., xxvi. p. 117, Taf.
vi. fig. 11.

Spongy disk lenticular, biconvex, in the darker centre much thicker than towards the thin periphery, with an irregular framework, without concentric rings, but with numerous piercing radial beams. Texture equal; meshes three to four times as broad as the bars.

_Dimensions._--Diameter of the disk 0.1 to 0.3, of the meshes 0.003 to 0.006.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface; also fossil in the Tertiary rocks of Sicily and Barbados.

4. _Spongodiscus favus_, Ehrenberg.

_Spongodiscus favus_, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d.
Wiss. Berlin, p. 301.

Spongy disk lenticular, biconvex, in the darker centre much thicker than towards the periphery, with an irregular framework, without concentric rings. Texture different, in the outer half with numerous radial beams and loose network, the meshes of which are three to four times as large as in the darker and denser framework of the centre.

_Dimensions._--Diameter of the disk 0.2, of the outer meshes 0.008 to 0.012, of the inner meshes 0.002 to 0.003.

_Habitat._--North Atlantic, Greenland, Færöe Channel (John Murray), surface.

5. _Spongodiscus biconcavus_, n. sp.

Spongy disk biconcave, in the peripheral, ring-like, thickened part twice as thick as in the hollowed central part, with an irregular framework, without concentric rings. Texture different, in the outer half looser than in the inner, darker part; meshes of the outer part five to six times, of the inner twice to three times, as broad as the bars.

_Dimensions._--Diameter of the disk 0.25, of the outer meshes 0.01 to 0.012, of the inner 0.004 to 0.006.

_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.

Subgenus 2. _Spongocyclia_, Haeckel, 1862, Monogr. d. Radiol., p. 469.

_Definition._--Spongy framework of the disk in the inner part with concentric, circular rings, in the outer part irregular.

{578}6. _Spongodiscus cycloides_, Haeckel.

_Spongodiscus cycloides_, Haeckel, 1860, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 843.

_Spongocyclia cycloides_, Haeckel, 1862, Monogr. d. Radiol., p. 469, Taf.
xxviii. fig. 1.

Spongy disk on both sides plain, in the central part with five to ten concentric, circular rings, in the peripheral part quite irregularly and densely spongy. Meshes twice to four times as broad as the bars.

_Dimensions._--Diameter of the disk 0.1 to 0.2, of the meshes 0.003 to 0.006.

_Habitat._--Mediterranean (Messina), North Atlantic (Canary Islands).

7. _Spongodiscus spongocyclia_, Haeckel.

_Spongocyclia triangularis_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 119,
Taf. vii. fig. 5.

Spongy disk lenticular, in the thicker central part with eleven to twelve circular, concentric rings, in the thinner, peripheral zone irregularly spongy. Meshes twice to four times as broad as the bars. (The triangular form in the specimen figured by Stöhr is accidental, produced by the broken margin.)

_Dimensions._--Diameter of the disk 0.2 to 0.3, of the meshes 0.006 to 0.008.

_Habitat._--Fossil in Tertiary rocks of Barbados (Haeckel) and Sicily (Stöhr).

Subgenus 3. _Spongospira_, Stöhr, 1880, Palæontogr., vol xxvi. p. 120.

_Definition._--Spongy framework of the disk in the inner part with spiral convolutions, in the outer part irregular.

8. _Spongodiscus florealis_, Haeckel.

_Spongospira florealis_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 120,
Taf. vii. fig. 6.

Spongy disk lenticular, in the thicker central part with five to six spiral convolutions, in the outer peripheral zone irregularly spongy. No radial beams piercing the framework. Meshes three to four times as broad as the bars.

_Dimensions._--Diameter of the disk 0.26, of the meshes 0.006 to 0.008.

_Habitat._--Fossil in Tertiary rocks of Sicily (Grotte), Stöhr.

9. _Spongodiscus spiralis_, n. sp.

_Spongospira spiralis_, Haeckel, 1881, Prodromus.

Spongy disk on both sides plain, with twelve to sixteen spiral convolutions in the central part, with irregular, spongy framework in the outer part, pierced by numerous interrupted radial beams. Meshes five to six times as broad as the bars.

_Dimensions._--Diameter of the disk 0.2 to 0.3, of the meshes 0.01 to 0.012.

_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms.

{579}Genus 254. _Spongophacus_,[293] Haeckel, 1881, Prodromus, p. 461.

_Definition._--#Spongodiscida# with a simple circular disk, without radial appendages, on the margin surrounded by a thin porous or solid equatorial girdle.

The genus _Spongophacus_, represented hitherto only by a single but interesting species, differs from _Spongodiscus_ by the peculiar girdle which surrounds the margin of the disk in the equatorial plane. It simulates the same formation as _Perichlamydium_ in the Porodiscida, and resembles also _Periphæna_, &c., in the Phacodiscida.

1. _Spongophacus periphæna_, n. sp.

Spongy disk lenticular, with an irregular, dense framework, in the centre darker than in the peripheral part. Margin of the disk very thin, surrounded by a broad, circular girdle, lying in the equatorial plane, about as broad as the half radius of the spongy disk. The inner part of the girdle is perforated by numerous irregular, small pores, which pass over gradually into the spongy meshes; the outer part is quite homogeneous, solid, transparent, with an extremely thin margin.

_Dimensions._--Diameter of the disk 0.2; breadth of the girdle 0.05.

_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms.

Subfamily 2. SPONGOTROCHIDA, Haeckel, 1881, Prodromus, p. 461.

_Definition._--#Spongodiscida# with a circular disk, the margin of which is armed with solid radial spines, situated in the equatorial plane (rarely also on both sides of the disk with radial spines).

Genus 255. _Spongolonche_,[294] Haeckel, 1881, Prodromus, p. 461.

_Definition._--#Spongodiscida# with two solid marginal spines, opposite in one equatorial diameter of the disk.

The genus _Spongolonche_ opens the series of the Spongotrochida, or of those Spongodiscida in which the margin of the disk is armed with solid radial spines, situated in the equatorial plane. _Spongolonche_ possesses only two such spines, opposite in one equatorial diameter of the disk; it corresponds therefore to _Stylocyclia_ among the Coccodiscida, to _Xiphodictya_ among the Porodiscida.

{580}1. _Spongolonche conostyla_, n. sp..

Spongy disk circular, with irregular framework, without concentric rings. Both opposite radial spines conical, about as long as the radius of the disk, and four times as long as broad at the base. Margin of the disk nearly smooth.

_Dimensions._--Diameter of the disk 0.16; length of the radial spines 0.18, basal thickness 0.045.

_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.

2. _Spongolonche amphistyla_, n. sp.

Spongy disk circular, with four to six concentric rings in the inner part, with quite an irregular framework in the outer part. Both opposite radial spines cylindrical, twice to three times as long as the diameter of the disk, at the base about as broad as two meshes of the framework. Margin of the disk ciliated.

_Dimensions._--Diameter of the disk 0.2; length of the radial spines 0.4 to 0.6, basal thickness 0.01.

_Habitat._--Pacific, central area, Station 271, depth 2425 fathoms.

Genus 256. _Spongotripus_,[295] Haeckel, 1881, Prodromus, p. 461.

_Definition._--#Spongodiscida# with three solid radial spines on the margin of the circular or triangular disk.

The genus _Spongotripus_ is characterised by three marginal spines, which are commonly regularly disposed, more rarely in a bilateral or an irregular manner. It corresponds to _Trigonocyclia_ among the Coccodiscida, to _Tripodictya_ among the Porodiscida.

Subgenus 1. _Spongotripodiscus_, Haeckel.

_Definition._--Radial spines of equal size and distance; triangle regular.

1. _Spongotripus regularis_, n. sp.

Spongy disk circular; three radial spines on its margin of equal size and equidistant, strong, conical, about as long as the diameter of the disk, and five times as long as broad at the base.

_Dimensions._--Diameter of the disk 0.15; length of the spines 0.16, basal breadth 0.03.

_Habitat._--Pacific, central area, Station 272, surface.

{581}2. _Spongotripus neumayri_, Haeckel.

_Spongechinus neumayri_, Dunikowski, 1882, Denskchr. d. k. Akad. d. Wiss.
Wien, xlv. p. 28, Taf. v. fig. 59.

Spongy disk circular, nearly spherical; three radial spines on its margin of equal size and equidistant, pyramidal, nearly as long as the diameter of the disk, and three times as long as broad at the base.

_Dimensions._--Diameter of the disk 0.15 to 0.2; length of the spines 0.11, basal breadth 0.04.

_Habitat._--Fossil in the Jura of the Alps and in Tertiary rocks of Barbados.

3. _Spongotripus strepsiceros_, n. sp.

Spongy disk circular; three radial spines on its margin of equal size and equidistant, angular, twice as long as the diameter of the disk, spirally twisted like the horns of Antilope strepsiceros.

_Dimensions._--Diameter of the disk 0.15; length of the spines 0.3, basal breadth 0.02.

_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.

Subgenus 2. _Spongotripodium_, Haeckel.

_Definition._--Radial spines of different size or at different distances; triangle either isosceles or irregular.

4. _Spongotripus ypsilon_, n. sp.

Spongy disk triangular, isosceles, with convex sides; three spines angular, of different size and at different distances; the odd spine straight and twice as long as the two paired spines, which are more approximated and curved concavely one to the other, like y.

_Dimensions._--Diameter of the disk 0.12; length of the odd spine 0.2, of the paired spines 0.1, basal breadth 0.04.

_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms.

5. _Spongotripus irregularis_, n. sp.

Spongy disk circular; three spines conical, irregularly curved, all three of different size, and at irregular distances; once to three times as long as the diameter of the disk; margin of the disk thorny.

_Dimensions._--Diameter of the disk 0.1; length of the spines 0.1 to 0.3, basal breadth 0.05.

_Habitat._--South Pacific, Station 300, depth 1375 fathoms.

{582}Genus 257. _Spongostaurus_,[296] Haeckel, 1881, Prodromus, p. 461.

_Definition._--#Spongodiscida# with four solid radial spines on the margin of the circular or square disk, commonly crossed in two equatorial diameters perpendicular one to another.

The genus _Staurodictya_ exhibits four marginal spines in cross form. Commonly the cross is regular and rectangular, the four spines being opposite in pairs in two perpendicular diameters; sometimes more or less irregular. The genus repeats _Staurodictya_ among the Porodiscida, _Staurocyclia_ among the Coccodiscida.

1. _Spongostaurus cruciatus_, n. sp.

Spongy disk circular; four radial spines on its margin opposite in two crossed equatorial diameters, perpendicular one to another, conical, about as long as the diameter of the disk.

_Dimensions._--Diameter of the disk 0.16; length of the spines 0.18, basal breadth 0.04.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.

2. _Spongostaurus serratus_, n. sp.

Spongy disk circular; four crossed radial spines very large, twice to three times as long as the diameter of the central disk, serrated on both edges, with two rows of strong conical perpendicular teeth (similar to the saw of _Pristis antiquorum_).

_Dimensions._--Diameter of the disk 0.1; length of the spines 0.2 to 0.3, breadth 0.02.

_Habitat._--Indian Ocean, Madagascar, Rabbe, surface.

3. _Spongostaurus hastatus_, n. sp.

Spongy disk square, with concave sides; four crossed radial spines cylindrical, on the broader distal end spear-shaped or nearly lanceolate, one and a half times as long as the diameter of the disk.

_Dimensions._--Diameter of the disk 0.13; length of the spines 0.2, basal breadth 0.01, distal breadth 0.03.

_Habitat._--Tropical Atlantic, Station 347, surface.

4. _Spongostaurus quadratus_, n. sp.

Spongy disk square, with rectilinear sides; four crossed radial spines pyramidal, arising from the corners of the square, about as long as its half diagonal.

_Dimensions._--Diameter of the disk 0.16; length of the spines 0.08, basal breadth 0.02.

_Habitat._--Pacific, central area, Station 271, surface.

{583}Genus 258. _Stylotrochus_,[297] Haeckel, 1862, Monogr. d. Radiol., p. 463.

_Definition._--#Spongodiscida# with numerous solid radial spines on the margin of the disk (five to ten or more), all situated in the equatorial plane.

The genus _Stylotrochus_ comprises those Spongodiscida in which the margin of the circular disk bears numerous radial spines. All these spines lie in the same equatorial plane, whilst in the following genus they are disposed over the whole surface of the disk. _Stylotrochus_ corresponds to _Astrocyclia_ among the Coccodiscida, to _Stylodictya_ among the Porodiscida. The spongy framework of the disk is either quite irregular (_Stylotrochiscus_), or includes in the middle part some concentric circular rings (_Stylospongia_).

Subgenus 1. _Stylotrochiscus_, Haeckel.

_Definition._--Spongy framework of the whole disk irregular, without concentric circular rings or spiral convolutions.

1. _Stylotrochus arachnius_, Haeckel.

_Spongotrochus arachnius_, Haeckel, 1862, Monogr. d. Radiol., p. 464.

Spongy framework of the whole disk irregular. Eight to twelve marginal spines very long and thin, bristle-shaped, twice to four times as long as the diameter of the disk. (Very similar to the common _Stylodictya arachnia_, but without concentric circular rings and sieve-plates, with quite irregular network of fine bars.)

_Dimensions._--Diameter of the disk 0.12 to 0.15; length of the radial spines 0.2 to 0.6, basal breadth 0.001.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface; also fossil in Tertiary rocks of Barbados and the Mediterranean.

2. _Stylotrochus craticulatus_, Haeckel.

_Spongotrochus craticulatus_, Stöhr, 1880, Palæontogr., vol. xxvi. p.
118, Taf. vi. fig. 12.

? _Spongodiscus aculeatus_, Ehrenberg, 1854, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 246.

Spongy framework of the whole disk irregular. Sixteen to twenty short marginal spines (twice to four times as long as the diameter of one mesh of the framework), free prolongations of internal radial beams which arise from the darker centre of the disk. (The interruption of the disk-margin on one point of its circumference, figured by Stöhr as osculum or "Mündungs-Oeffnung," is probably an accidental abnormality; I did not find it in other specimens.)

{584}_Dimensions._--Diameter of the disk 0.2 to 0.25; length of the radial spines 0.005 to 0.018, basal breadth 0.001 to 0.003.

_Habitat._--Pacific, central area, Stations 266 to 268, surface; fossil in Barbados and Sicily.

3. _Stylotrochus helianthus_, n. sp.

Spongy framework of the whole disk irregular. Thirty to fifty very large, conical radial spines, about as long as the diameter of the disk, and at the base two to four times as broad as one mesh of the framework (without internal prolongations).

_Dimensions._--Diameter of the disk 0.15 to 0.2; length of the radial spines 0.16 to 0.24, basal breadth 0.008 to 0.016.

_Habitat._--Pacific, central area, Station 272, surface.

4. _Stylotrochus rhabdostylus_, Haeckel.

_Spongosphæra rhabdostyla_, Ehrenberg, 1875, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 256, Taf. xxvi. figs. 1, 2.

Spongy framework of the whole disk irregular. Four very large marginal primary spines crossed in two equatorial diameters, perpendicular one to another, and between them numerous (twelve to twenty or more) smaller secondary spines. The latter arise from the margin, whilst the former pierce the disk and are nearly united in its centre. All the spines are cylindrical, the smaller as broad as one mesh, the larger three to six times as broad.

_Dimensions._--Diameter of the disk 0.2; length of the four main spines 0.15 to 0.3, breadth 0.01 to 0.02; length of the accessory spines 0.05 to 0.1, breadth 0.005.

_Habitat._--Fossil in the rocks of Barbados.

5. _Stylotrochus heteracanthus_, Haeckel.

_Spongotrochus heteracanthus_, Haeckel, 1862, Monogr. d. Radiol., p. 464.

Spongy framework of the whole disk irregular. Ten very long needle-shaped marginal spines (symmetrically distributed), and between them numerous very fine, shorter, accessory, bristle-shaped spines.

_Dimensions._--Diameter of the disk 0.16; length of the main spines 0.16, basal breadth 0.002; length of the secondary spines 0.03.

_Habitat._--Mediterranean (Messina), surface.

Subgenus 2. _Stylospongia_, Haeckel, 1862, Monogr. d. Radiol., p. 473.

_Definition._--Spongy framework of the disk in the inner part with concentric rings or spiral convolutions, in the outer part quite irregular.

{585}6. _Stylotrochus huxleyi_, Haeckel.

_Stylospongia huxleyi_, Haeckel, 1862, Monogr. d. Radiol., p. 473, Taf.
xxviii. fig. 7.

Spongy framework of the disk in the inner part with five concentric rings, in the outer part quite irregular. Ten marginal spines, conical at the base, about as long as the radius of the disk, without inner piercing prolongations.

_Dimensions._--Diameter of the disk 0.12; length of the radial spines 0.06, basal breadth 0.003.

_Habitat._--Mediterranean (Messina), Haeckel.

7. _Stylotrochus geddesii_, n. sp. (Pl. 41, fig. 11).

_Stylospongidium geddesii_, Haeckel, 1881, Atlas (pl. xli. fig. 11).

Spongy framework of the disk in the inner part with four to eight concentric rings (or partially spiral convolutions), in the outer part quite irregular. Thirty to fifty pyramidal marginal spines of variable size, one-fourth to one-half as long as the radius of the disk, outer prolongations of inner piercing radial beams, which arise from various concentric rings. I call this interesting species, which is intermediate between _Stylodictya_ and _Stylotrochus_, in honour of the morphologist Mr. Patrick Geddes of Edinburgh.

_Dimensions._--Diameter of the disk 0.15 to 0.25; length of the radial spines 0.03 to 0.06, basal breadth 0.004 to 0.01.

_Habitat._--Pacific, central area, Stations 270 to 274, in 2350 to 2925 fathoms.

Genus 259. _Spongotrochus_,[298] Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 844.

_Definition._--#Spongodiscida# with numerous solid radial spines (five to ten or more), which are scattered over the whole surface and the margin of the disk, or regularly disposed on both sides of it.

The genus _Spongotrochus_ differs from the foregoing and nearly allied genus by the distribution of the numerous radial spines. These are not confined to the margin of the disk, but also scattered on its whole surface, and sometimes symmetrically disposed on both its sides in a regular manner. Also in this genus the spongy framework is sometimes quite irregular (_Spongotrochiscus_), at other times in the middle part with enclosed concentric rings (_Stylospongidium_).

Subgenus 1. _Spongotrochiscus_, Haeckel, 1862, Monogr. d. Radiol., p. 463.

_Definition._--Spongy framework of the whole disk irregular, without concentric rings or spiral convolutions.

{586}1. _Spongotrochus brevispinus_, Haeckel.

_Spongotrochus brevispinus_, Haeckel, 1862, Monogr. d. Radiol., p. 462,
Taf. xxvii. figs. 4, 5.

Spongy framework of the whole disk irregular, everywhere equal. The whole surface of the disk covered with numerous short, needle-shaped, radial spines, about as long as the thickness of the disk, which is one-fifth of its diameter.

_Dimensions._--Diameter of the disk 0.18; length of the radial spines 0.03 to 0.04, basal breadth 0.002.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

2. _Spongotrochus multispinus_, n. sp.

Spongy framework of the whole disk irregular, in the centre darker. The whole surface of the disk covered with numerous conical radial spines, about as long as the radius of the disk.

_Dimensions._--Diameter of the disk 0.22; length of the radial spines 0.1, basal breadth 0.008.

_Habitat._--Pacific, central area, Stations 271 to 274, surface.

3. _Spongotrochus longispinus_, Haeckel.

_Spongotrochus longispinus_, Haeckel, 1862, Monogr. d. Radiol., p. 463,
Taf xxvii. figs. 2, 3.

Spongy framework of the whole disk irregular, everywhere equal. Surface thorny. Twenty long, needle-shaped, radial spines, about as long as the diameter of the disk, symmetrically distributed in pairs on both flat sides of the disk, so that the opposite pairs lie in five equidistant, meridian planes (compare the figures).

_Dimensions._--Diameter of the disk 0.2; length of the twenty radial spines 0.2, basal breadth 0.001.

_Habitat._--Mediterranean (Messina), surface.

Subgenus 2. _Stylospongidium_, Haeckel, 1881, Prodromus, p. 460.

_Definition._--Spongy framework of the disk in the inner part with concentric rings or spiral convolutions, in the outer part quite irregular.

4. _Spongotrochus scutella_, n. sp.

_Spongotrochus ehrenbergii_, Bütschli, 1882, L. N. 41, Taf. xxvi. figs.
1_a_, 1_b_.

Spongy framework of the disk in the inner part with four to six concentric rings, in the outer part quite irregular. The whole surface of the disk covered with bristle-shaped radial spines, about half as long as the radius of the disk.

_Dimensions._--Diameter of the disk 0.24; length of the radial spines 0.06, basal breadth 0.02.

_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms.

{587}5. _Spongotrochus parma_, n. sp.

Spongy framework of the disk in the inner part with five to eight spiral convolutions (or partly concentric rings), in the outer part quite irregular. Thirty to forty long, bristle-shaped, radial spines, about as long as the diameter of the disk, disposed on both flat sides of the disk, but not on the margin.

_Dimensions._--Diameter of the disk 0.16; length of the radial spines 0.18, basal breadth 0.003.

_Habitat._--South Atlantic, Station 325, surface.

Subfamily 3. SPONGOBRACHIDA, Haeckel, 1881, Prodromus, p. 461.

_Definition._--#Spongodiscida# with two or more (commonly three or four) spongy radial arms on the margin of the disk, situated in its equatorial plane (with or without a connecting patagium between the arms).

Genus 260. _Spongolena_,[299] n. gen.

_Definition._--#Spongodiscida# with two opposite spongy arms on the margin of the disk, without a connecting patagium.

The genus _Spongolena_ opens the series of the Spongobrachida, or of the Spongodiscida provided with radial spongy arms on the margin of the disk. _Spongolena_ is the most simple form of this subfamily, and bears only two simple opposite arms, without a connecting patagium. It corresponds to _Amphibrachium_ (Porodiscida) and to _Diplactura_ (Coccodiscida). Also there is no patagium. _Spongolena_ may easily be confounded with _Spongurus_ (compare my Prodromus, 1881, p. 461); but in the true _Spongurus_ (an ellipsoid) the transverse section is circular, in _Spongolena_ elliptical.

1. _Spongolena rhopalura_, n. sp.

Arms club-shaped, three times as long as broad, at the rounded distal end twice as broad as at the base, and twice as long as the diameter of the circular central disk. Surface nearly smooth.

_Dimensions._--Radius of the arms (or the distance from the centre to the distal arm-end) 0.16, distal breadth 0.05, basal breadth 0.03.

_Habitat._--Pacific, central area, Station 273, depth 2350 fathoms.

2. _Spongolena spongura_, n. sp.

Arms nearly cylindrical, twice as long as broad, and a little longer than the diameter of the elliptical central disk. Surface thorny, some longer bristle-shaped spines on the distal end of the {588}arms. (Very similar to the ellipsoid _Spongurus cylindricus_, Monogr. d. Radiol., p. 465, Taf. xxvii. fig. 1, but differs in the compressed lenticular (not ellipsoidal) form of the central disk; the transverse section of the arm is elliptical, not circular.)

_Dimensions._--Radius of the arms 0.1, breadth 0.04.

_Habitat._--Pacific, central area, Station 270, depth 2925 fathoms.

3. _Spongolena cypselura_, n. sp.

Arms nearly triangular, not longer than broad, about half as large as the elliptical central disk, at the broader distal end with two very large, widely divergent lateral spines, and between them several smaller, like the tail of a swallow. Surface thorny.

_Dimensions._--Radius of the arms 0.2, distal breadth (without spines) 0.15, basal breadth 0.07.

_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.

Genus 261. _Spongobrachium_,[300] Haeckel, 1881, Prodromus, p. 461.

_Definition._--#Spongodiscida# with two opposite spongy arms on the margin of the disk, connected by a spongy patagium of different texture.

The genus _Spongobrachium_ differs from the foregoing only in the loose spongy patagium, which envelops both opposite spongy arms. It corresponds to _Amphymenium_ among the Porodiscida and to _Amphiactura_ among the Coccodiscida.

1. _Spongobrachium ellipticum_, Haeckel.

_Spongocyclia elliptica_, Haeckel, 1862, Monogr. d. Radiol., p. 470, Taf.
xxviii. fig. 2.

_Spongodiscus ellipticus_, Haeckel, 1860, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 844.

Arms nearly square, scarcely as long and broad as the radius of the circular central disk, at the broader distal end truncated. Patagium complete, enveloping the whole disk with the arms, and forming a larger elliptical disk of looser framework. (In my Monograph, 1862, _loc. cit._, I had not distinguished the opposite darker arms, opposite in the longer axis of the elliptical disk, from the enveloping looser framework of the patagium. In larger specimens of the Challenger collection this distinction is very evident.)

_Dimensions._--Radius of the arms 0.12, breadth 0.05; major axis of the elliptical patagium 0.24, minor 0.16.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

2. _Spongobrachium lanceolatum_, n. sp.

Arms club-shaped, twice as long as broad, at the distal end pointed, five times as long as the radius of the circular central disk. Patagium complete, enveloping the whole disk with the arms, {589}and forming a larger lanceolate disk of looser framework. (Similar in form to _Amphymenium pupula_, Pl. 44, fig. 8, but with an irregular spongy framework and pointed ends.)

_Dimensions._--Radius of the arms 0.16, breadth 0.05; major axis of the lanceolate patagium 0.32, minor axis 0.12.

_Habitat._--Pacific, central area, Station 270, surface.

Genus 262. _Rhopalodictyum_,[301] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 830.

_Definition._--#Spongodiscida# with three spongy arms on the margin of the circular or triangular disk, without a connecting patagium.

The genus _Rhopalodictyum_ comprises those very common forms of Spongodiscida in which the margin of the disk is provided with three simple, free, spongy arms. It corresponds to _Dictyastrum_ and _Rhopalastrum_ among the Porodiscida, to _Trigonactura_ among the Coccodiscida. The typical species of this genus is _Rhopalodictyum abyssorum_ of Ehrenberg, the only species figured by him. His diagnosis of the genus was very insufficient, and agreed with that of his _Dictyastrum_ (compare above the improved diagnosis of this genus, p. 526, and my Monograph, p. 466).

Subgenus 1. _Rhopalodictya_, Haeckel.

_Definition._--Triangular shell regular, with three arms of equal size and equidistant.

1. _Rhopalodictyum abyssorum_, Ehrenberg.

_Rhopalodictyum abyssorum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 299, Taf. viii. fig. 17.

Arms of equal size and equidistant, club-shaped, about as long as the diameter of the triangular central disk, and a little longer than the breadth of the pear-shaped rounded distal end. Surface rough.

_Dimensions._--Radius of the arms 0.11, basal breadth 0.03, distal breadth 0.06.

_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific; tropical zone, surface.

2. _Rhopalodictyum truncatum_, Ehrenberg.

_Rhopalodictyum truncatum_, Ehrenberg, 1861, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 301.

? _Dictyastrum angulatum_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 289, Taf. viii. fig. 18.

Arms of equal size and equidistant, nearly square, with straight edges, towards the truncated end a little broader, about of the same diameter as the central triangular disk. This species is indicated {590}by Ehrenberg only by the short diagnosis, "Radiis stellæ tribus apice truncatis." It is probably identical with his figure of _Dictyastrum angulatum_ (_loc. cit._). This latter name I have retained for the similar Porodiscid (above, p. 526), mainly because the genera _Dictyastrum_ and _Rhopalodictyum_, according to the insufficient diagnosis of Ehrenberg, seem to be identical. (Compare my Monograph, 1862, p. 466.)

_Dimensions._--Radius of each arm 0.13, basal breadth 0.09, distal breadth 0.1.

_Habitat._--Tropical Pacific, Philippine Sea, Station 200, depth 250 fathoms; Atlantic (Mexican Gulf Stream).

3. _Rhopalodictyum subacutum_, Ehrenberg.

_Rhopalodictyum subacutum_, Ehrenberg, 1861, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 301.

Arms of equal size and equidistant, club-shaped, three times as long as the diameter of the central disk, which equals the breadth of the thickened distal end; the latter is armed with a strong pyramidal terminal spine. (The diagnosis of Ehrenberg is "Radiis stellæ tribus, apice cuneatis subacutis.")

_Dimensions._--Radius of the arms 0.2, basal breadth 0.04, distal breadth 0.07.

_Habitat._--North Atlantic, surface and various depths; Greenland; Mexican Gulf Stream; Færöe Channel (John Murray).

4. _Rhopalodictyum bifidum_, n. sp.

Arms of equal size and equidistant, in the distal half forked, twice as long as the diameter of the central disk; both fork branches half as broad as the simple basal part, truncated at the distal end.

_Dimensions._--Radius of the arms 0.16, basal breadth 0.08, distal breadth 0.04.

_Habitat._--North Pacific, Station 237, surface.

Subgenus 2. _Triactinosphæra_, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, vol. 45, ii. p. 192.

_Definition._--Triangular shell bilateral or irregular, with three arms of different size or distance.

5. _Rhopalodictyum zittelii_, Haeckel.

_Triactinosphæra zittelii_, Dunikowski, 1882, Denkschr. d. k. Akad. d.
Wiss, Wien, vol. 45, ii. p. 192.

Arms of different size and at unequal distances, one odd arm being a little shorter than the two paired arms; the odd angle between the latter is larger than the paired angles between them and the {591}former. Arms club-shaped, their basal semi-cylindrical, half as broad as the spherical distal half, which bears a strong, conical, terminal spine. The discoverer of this remarkable, very old, Liassic species, Dunikowski, supposes that it is not a true Discoid, from the absence of a central disk; in my opinion the central disk (nearly spherical) has the same relation to the arms as in many other #Discoidea#, their equatorial plane is the same.

_Dimensions._--Radius of the odd arm 0.18, of the paired arms 0.24; basal breadth 0.08, distal breadth 0.16.

_Habitat._--Fossil in the Alpine Lias, Schafberg, near Salzburg, Dunikowski.

6. _Rhopalodictyum elongatum_, n. sp.

Arms of different size and at unequal distances, one odd arm being twice as long as both paired arms; the odd angle between the latter much larger than both equal paired angles. Arms nearly cylindrical, little flattened, three to six times as long as broad, with rounded blunt distal end.

_Dimensions._--Radius of the arms 0.15 to 0.3, breadth 0.05.

_Habitat._--Pacific, central area, Station 274, surface.

7. _Rhopalodictyum curvatum_, n. sp.

Arms of different size and at unequal distances, irregular, more or less curved, nearly cylindrical, five to ten times as long as broad, with rounded blunt distal end. (There were observed only two specimens of this remarkable irregular species; in one specimen all three arms were simple, in the other one odd arm forked. The length of the arms and the size of the angles between them seems to be very different and variable.)

_Dimensions._--Radius of the arms 0.3 to 0.6 to 1.15, breadth 0.06 to 0.12.

_Habitat._--Pacific, central area, Station 271, surface.

Genus 263. _Dictyocoryne_,[302] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 830.

_Definition._--#Spongodiscida# with three spongy arms on the margin of the circular or triangular disk, connected by a spongy patagium of different texture.

The genus _Dictyocoryne_ differs from the foregoing _Rhopalodictyum_ only in the patagium, connecting the three spongy arms, and bears to it the same relation as in the Porodiscida _Euchitonia_ does to _Rhopalastrum_. The typical species of this genus is _Dictyocoryne profunda_, the only species figured by Ehrenberg. After his {592}insufficient diagnosis _Dictyocoryne_ was identical with his _Spongaster_ (compare my Monograph, p. 467); but as the type of this latter genus (_Spongaster tetras_) figured by him, 1872, had four crossed arms, we retain this genus here separate.

Subgenus 1. _Dictyocorynula_, Haeckel.

_Definition._--Triangular shell regular, with three arms of equal size and equal distance.

1. _Dictyocoryne profunda_, Ehrenberg.

_Dictyocoryne profunda_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 307, Taf. vii. fig. 23.

Arms of equal size and equidistant, club-shaped, in the outer circular half three times as broad as in the inner cylindrical half, and much larger than the small triangular central disk. Patagium complete, forming an equilateral triangle with rounded corners.

_Dimensions._--Radius of the arms 0.14, basal breadth 0.025, distal breadth 0.07.

_Habitat._--Pacific, Philippine Sea, depth 3300 fathoms, Ehrenberg; Station 198, depth 2150 fathoms; Station 274, depth 2750 fathoms.

2. _Dictyocoryne tetradiscus_, n. sp.

Arms of equal size and equidistant, club-shaped, their outer circular half is quite as large as the circular central disk, and is connected with it by the thin cylindrical inner half, which is scarcely one-fourth as broad. Patagium complete, forming an equilateral triangle with rounded corners and convex sides.

_Dimensions._--Radius of the arms 0.16, basal breadth 0.02, distal breadth 0.08.

_Habitat._--Pacific, central area, Stations 271 to 274, in 2350 to 2750 fathoms.

3. _Dictyocoryne euchitonia_, Haeckel.

_Dictyocoryne euchitonia_, Haeckel, 1862, Monogr. d. Radiol., p. 468.

Arms of equal size and equidistant, lanceolate, twice as long as broad in the distal part, and three times as long as the small circular central disk. Patagium complete, forming an equilateral triangle with pointed corners. (Very similar to _Euchitonia köllikeri_, Monograph, 1862, p. 511, Taf. xxxi. fig. 6, but quite spongy, not concentric.)

_Dimensions._--Radius of the arms 0.15, basal breadth 0.03, distal breadth 0.06.

_Habitat._--Mediterranean (Messina), Haeckel.

{593}4. _Dictyocoryne trigona_, n. sp.

Arms of equal size and equidistant, lanceolate, three times as long as broad in the middle part, and as the diameter of the triangular central disk; their distal end armed with a strong conical radial spine. Patagium complete, forming an equilateral triangle with pointed corners.

_Dimensions._--Radius of the arms 0.2, basal breadth 0.02, distal breadth 0.06.

_Habitat._--North Atlantic, Canary Islands, surface.

Subgenus 2. _Dictyocorynium_, Haeckel.

_Definition._--Triangular shell bilateral or irregular, with three arms of different sizes or at different distances.

5. _Dictyocoryne charybdaea_, Haeckel.

_Spongocyclia charybdaea_, Haeckel, 1862, Monogr. d. Radiol., p. 472,
Taf. xxviii. figs. 5, 6.

_Spongodiscus charybdaeus_, Haeckel, 1860, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 844.

Arms at different distances, nearly equilateral triangular, scarcely half as long as the radius of the large circular central disk. Both paired arms touching at their bases, separated by a great distance from the opposite odd arm. Patagium complete, nearly pentagonal. (The illustration in my Monograph, in the coloured plate xxviii., is better than my description, as I had not exactly separated the arms from the patagium.)

_Dimensions._--Radius of the arms 0.18, basal breadth 0.08.

_Habitat._--Mediterranean (Messina), surface.

6. _Dictyocoryne pentagona_, Stöhr.

_Dictyocoryne pentagona_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 118,
Taf. vii. fig. 2.

Arms at different distances, club-shaped, little longer than broad at their rounded distal end. Both paired arms smaller and more approximate than the opposite odd arm. Patagium complete, very large, enveloping the whole shell, and forming a pentagon with rectilinear base and transverse constriction, and with five rounded corners.

_Dimensions._--Radius of the arms 0.1 to 0.15, middle breadth 0.04.

_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.

7. _Dictyocoryne agrigentina_, Stöhr.

_Dictyocoryne agrigentina_, Stöhr, 1880, Palæontogr., vol. xxvi. p. 118,
Taf. vii. fig. 1.

Arms at different distances, club-shaped, about twice as long as broad, and smaller than the large triangular central disk. Both paired arms smaller and more approximate than the opposite odd {594}arm. Patagium incomplete, enveloping only the basal half of the arms as a circular spongy disk of loose framework.

_Dimensions._--Radius of the arms 0.18, basal breadth 0.05, distal breadth 0.08.

_Habitat._--Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.

8. _Dictyocoryne echinata_, n. sp.

Arms unequal and at different distances, club-shaped, in the distal half twice as broad as in the basal half, three times as long as the small triangular central disk, at their distal end armed with one larger and several smaller conical spines. Both paired arms with touching bases, and only half as large as the doubly remote odd arm. Patagium incomplete, enveloping only the basal half of the arms, and forming a circular disk of looser framework. Surface thorny.

_Dimensions._--Radius of the arms 0.15 to 0.2, basal breadth 0.03, distal breadth 0.06.

_Habitat._--South Atlantic, Station 325, surface.

Genus 264. _Spongasteriscus_,[303] Haeckel, 1862, Monogr. d. Radiol., p. 474 (_sensu restricto_).

_Definition._--SPONGODISCIDA with four spongy arms on the margin of the circular or quadrangular disk, crossed in two equatorial diameters, without a connecting patagium.

The genus _Spongasteriscus_ (in the restricted definition here stated) exhibits on the margin of the disk four spongy arms, which form either a regular or a bilateral cross. It corresponds to _Stauralastrum_ and _Myelastrum_ among the Porodiscida, to _Astractura_ among the Coccodiscida.

Subgenus 1. _Spongasteriscinus_, Haeckel.

_Definition._--Cross formed by the four arms regular, rectangular, with equal-sized and equidistant arms.

1. _Spongasteriscus ovatus_, n. sp.

Arms at equal distances, forming a regular, rectangular cross, egg-shaped, with a broader rounded distal end, one and a third times as long as broad, and three times as long as the radius of the central disk; in the latter three to four concentric rings.

_Dimensions._--Radius of the arms 0.1, greatest breadth 0.06.

_Habitat._--Western Tropical Pacific, Station 225.

{595}2. _Spongasteriscus clavatus_, n. sp.

Arms at equal distances, forming a regular, rectangular cross, club-shaped, about as long as the diameter of the central disk, and at their rounded distal end one and a third times as long as broad, at their narrow base only one third as broad. In the centre five to six concentric rings.

_Dimensions._--Radius of the arms 0.13, distal breadth 0.06, basal breadth 0.02.

_Habitat._--Pacific, central area. Station 271, surface.

3. _Spongasteriscus mucronatus_, n. sp.

Arms at equal distances, forming a regular, rectangular cross, club-shaped, three times as long as the radius of the central disk, in the distal half nearly circular, three to four times as broad as at the narrow base. The rounded distal end armed with a strong pyramidal spine. In the centre no concentric rings. (Similar to _Stauralastrum rhopalophorum_, Pl. 45, fig. 1, but quite spongy.)

_Dimensions._--Radius of the arms 0.12, basal breadth 0.03, distal breadth 0.02.

_Habitat._--Pacific, central area, Station 265, depth 2900 fathoms.

4. _Spongasteriscus furcatus_, n. sp.

Arms at equal distances, forming a regular, rectangular cross, in the distal third forked; both fork branches half as long as the basal undivided part of the arm, which is twice as long as broad. Distal ends of the eight branches blunt, rounded. In the central disk no concentric rings.

_Dimensions._--Radius of the arms 0.12, basal breadth 0.03; distal breadth of the branches 0.02.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.

5. _Spongasteriscus armatus_, n. sp.

Arms at equal distances, forming a rectangular, regular cross, in the distal half forked; both fork branches of the same length as the basal undivided part of the arm, which is nearly square. Distal ends of the eight branches armed with a strong pyramidal spine. In the central disk no concentric rings. (Similar to _Dicranastrum cornutum_, Pl. 45, fig. 2, but quite spongy.)

_Dimensions._--Radius of the arms 0.18, basal breadth 0.03, distal breadth 0.015.

_Habitat._--South Pacific, Station 295, depth 1500 fathoms.

Subgenus 2. _Spongasterisculus_, Haeckel.

_Definition._--Cross formed by the four arms, bilateral or irregular, with the arms at different distances.

{596}6. _Spongasteriscus quadricornis_, Haeckel.

_Spongasteriscus quadricornis_, Haeckel, 1862, Monogr. d. Radiol., p.
474, Taf. xxviii. figs. 8-10.

_Spongodiscus quadricornis_, Haeckel, 1860, Monatsber. d. k. preuss.
Akad. d. Wiss. Berlin, p. 844.

Arms at different distances, forming a bilateral or irregular cross, grouped in two opposite pairs; their form equilateral triangular; their length smaller than the radius of the large circular central disk, which exhibits in the interior eight to sixteen concentric rings.

_Dimensions._--Radius of the arms 0.2, of the central disk 0.13; basal breadth of the arms 0.08.

_Habitat._--Mediterranean (Messina), Haeckel, surface.

7. _Spongasteriscus tetraceros_, Haeckel.

_Spongasteriscus tetraceros_, Haeckel, 1862, Monogr. d. Radiol., p. 475.

Arms at different distances, forming a bilateral or irregular cross, grouped in two opposite pairs; their form isosceles triangular; their length larger than the radius of the large elliptical central disk, which exhibits in the interior six to twelve concentric rings.

_Dimensions._--Radius of the arms 0.16, of the central disk 0.1; basal breadth of the arms 0.06.

_Habitat._--Mediterranean (Messina), North Atlantic (Canary Islands), surface.

8. _Spongasteriscus myelastrum_, n. sp.

Arms at different distances, forming a bilateral or irregular cross, grouped in two opposite pairs; the arms of one pair broader and shorter than the arms of the other pair. Each arm in its basal half simple, in the distal half forked; ends of the fork branches blunt. In the central disk no concentric rings. (Similar to _Myelastrum octocorne_, Pl. 47, fig. 12, but quite spongy.)

_Dimensions._--Radius of the arms 0.2, basal breadth 0.05, distal breadth 0.02.

_Habitat._--North Pacific, Station 236, surface.

Genus 265. _Spongaster_,[304] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 833.

_Definition._--#Spongodiscida# with four spongy arms on the margin of the circular or quadrangular disk, connected by a spongy patagium of different texture.

The genus _Spongaster_ differs from the foregoing _Spongasteriscus_ in the patagium connecting the spongy arms, and bears therefore to it the same relation as, in the Porodiscida, _Histiastrum_ does to _Stauralastrum_, or, in the Coccodiscida, _Stauractura_ does to _Astractura_. The typical specimen, figured by Ehrenberg (_Spongaster tetras_), exhibits a regular, square disk, as also some other species. In a certain number of other species (formerly united by me with _Spongocyclia_) the quadrangular disk is bilateral.

{597}Subgenus 1. _Spongastrella_, Haeckel.

_Definition._--Cross formed by the four arms regular, rectangular, with the arms of equal size and equidistant.

1. _Spongaster tetras_, Ehrenberg.

_Spongaster tetras_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
Berlin, p. 299, Taf. vi. (iii.) fig. 8.

_Dictyocoryne tetras_, Haeckel, 1862, Monogr. d. Radiol., p. 469.

Arms at equal distances, forming a rectangular, regular Myelastrum, papiliocross, club-shaped, about twice as long as the diameter of the square central disk and eight times as long as broad at their base. Distal ends rounded, perfectly enclosed by the complete patagium, which forms a regular square, with slightly concave sides.

_Dimensions._--Radius of the arms 0.12, distal breadth 0.03, basal breadth 0.015; length of the square side 0.2.

_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, surface and in various depths.

2. _Spongaster quadratus_, n. sp.

Arms at equal distances, forming a regular, rectangular cross, club-shaped, about four times as long as the diameter of the central circular disk, and five times as long as broad at the base. Basal third of the arms square; distal two thirds triangular, three times as broad, with a truncated distal end. Patagium complete, perfectly enveloping the arms, and bordered by an elegant, radially striated, broad edge, forming a regular square. (Similar to _Histiastrum quadratum_, Pl. 46, fig. 4, but quite spongy.)

_Dimensions._--Radius of the arms 0.15, distal breadth 0.06, basal breadth 0.02; length of the square side 0.25.

_Habitat._--Pacific, central area, Stations 270 to 274, depths 2350 to 2925 fathoms.

3. _Spongaster cruciatus_, n. sp.

Arms at equal distances, forming a rectangular, regular cross, lanceolate, three times as long as broad and as the diameter of the central circular disk. Ends of the arms provided with a short conical spine. Patagium incomplete, enveloping only the basal half of the arms, forming a regular square with concave sides.

_Dimensions._--Radius of the arms 0.18, greatest breadth 0.05; length of the square side 0.2.

_Habitat._--South Pacific, Station 288, surface.

{598}4. _Spongaster pentacyclus_, n. sp.