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, 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.

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. , 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.

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. , 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. , 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 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, 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. , 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 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. , 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. , but is a true Discoid, no Prunoid.) Compare also Pl. , 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. , 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. , 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.

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, 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. , 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. , 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.

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. , 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. , 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. , 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, 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.

Subgenus 1. Amphicraspedon, Haeckel.

Definition.—Both arms of equal size and form, without terminal spines of the branches.

1. Amphicraspedum maclaganium, n. sp. (Pl. , 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. , 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. , 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, 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, 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.

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. , 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. , 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. , 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.

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. , 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, 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 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. , 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. , 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.

5. Rhopalastrum ypsilinum, n. sp. (Pl. , 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. , 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.

9. Rhopalastrum triceros, n. sp. (Pl. , 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. , 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. , 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, 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, 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.

4. Hymeniastrum euclidis, n. sp. (Pl. , 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. .)

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. , 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.

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, 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.

The genus Euchitonia, quite insufficiently characterised by Ehrenberg, was founded by him (1860) for one single species, afterwards (1872) described and figured as Euchitonia furcata. Retaining this species correctly as the type of this genus, I give to it here the above diagnosis. In my Monograph (1862, p. 503) I described seven Mediterranean species of Euchitonia. Three of these have in common the characters according to the present diagnosis: Euchitonia mülleri, Euchitonia virchowii, Euchitonia beckmanni; two others appertain (on account of the regular, not bilateral form) to Hymeniastrum, and two others (on account of the forked, not simple arms) to Trigonastrum. Afterwards (1880) three true fossil species of Euchitonia were described by Stöhr (Euchitonia cruciata, Euchitonia zittelii, and Euchitonia acuta). Some species of this genus are cosmopolitan, and appertain to the most common and everywhere represented Discoidea.

Subgenus 1. Stylactis, Ehrenberg, 1872 (loc. cit.).

Definition.—Arms with blunt ends, without terminal spines.

1. Euchitonia furcata, Ehrenberg.

Euchitonia furcata, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 308; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. vi. iii. fig. 6.

Distance between the paired arms about half as large as their distance from the odd arm. All three arms nearly of the same size and form, about twice as long as broad, one and a half times at the blunt convex end as broad as at the base. Patagium incomplete, with concave chamber-rows and irregular network, only enveloping the basal half of the arms.

Dimensions.—Radius of all three arms 0.15, basal breadth of each arm 0.04, terminal breadth 0.06.

Habitat.—North Pacific, Californian Sea, depth 2600 fathoms, Ehrenberg.

2. Euchitonia mülleri, Haeckel.

Euchitonia mülleri, Haeckel, 1862, Monogr. d. Radiol., p. 508, Taf. xxx. figs. 5-10.

Euchitonia mülleri, Stöhr, 1880, Palæontogr., vol. xxvi. p. 110, Taf. v. fig. 5.

Distance between the paired arms about two-thirds as large as their distance from the odd arm, which is somewhat larger. Length of the arms equals two and a half times the breadth of the blunt convex end or five times the breadth of the base. Patagium with concave chamber-rows, nearly complete, enveloping the arms with exception of the terminal face. (This common species is very variable; compare my Monograph.)

Dimensions.—Radius of all three arms 0.16 to 0.22, basal breadth 0.03 to 0.05, terminal breadth 0.06 to 0.08.

Habitat.—Cosmopolitan; one of the most common Discoidea in all seas, on the surface as well as at different depths; also fossil in the Tertiary rocks of Barbados and Sicily.

3. Euchitonia triangulum, Haeckel.

Stylactis triangulum, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 320; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. viii. fig. 9.

Stylactis triangulum, Stöhr, 1880, Palæontogr., vol. xxvi. p. 113, Taf. vi. fig. 2.

Distance between the paired arms about two-thirds as large as their distance from the odd arm. All three arms nearly of the same size and form, about one and a half times as long as broad, nearly as broad at the base as at the blunt rounded end. Patagium incomplete, with convex chamber-rows, enveloping about two-thirds of the arms.

Dimensions.—Radius of all three arms 0.15, basal breadth 0.05, terminal breadth 0.06.

Habitat.—Pacific and Atlantic, Stations 253, 272, 354, surface; also fossil in the Tertiary rocks of Barbados and Sicily.

4. Euchitonia cruciata, Stöhr.

Euchitonia cruciata, Stöhr, 1880, Palæontogr., vol. xxvi. p. 111, Taf. v. fig. 7.

Distance between the paired arms about one and a half times as large as their distance from the odd arm, which is a little larger. Length of the arm nearly equals twice the breadth, which is the same at the base and at the rounded blunt ends. Patagium incomplete, with concave chamber-rows, enveloping only the base of the arms, and forms between them three other smaller arms; therefore the whole shell forms six angles with six alternating arms.

Dimensions.—Radius of all three arms 0.15, basal breadth 0.05.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

5. Euchitonia lanceolata, n. sp. (Pl. , fig. 9).

Distance between the paired arms about one and a third times as large as their distance from the odd arm. All three arms nearly of the same size and form, three times as long as broad, lanceolate, much broader in the middle part than at both ends; distal end cuspidate, but not spiny. Patagium incomplete, with convex chamber-rows, envelops about two-thirds of the arms.

Dimensions.—Radius of all three arms 0.18, greatest breadth (in the width) 0.06.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

6. Euchitonia zittelii, Haeckel.

Stylactis zittelii, Stöhr, 1880, Palæontogr., vol. xxvi. p. 112, Taf. v. fig. 8.

Distance between the paired arms about one-fifth as large as their distance from the odd arm. All three arms nearly of the same size and form, in the proximal half thinner and nearly square, in the distal half thicker and circular; the latter half twice to three times as broad as the former. Patagium incomplete, with convex chamber-rows, envelops only the proximal square half of the arms.

Dimensions.—Radius of all three arms 0.15, basal breadth 0.03, terminal breadth 0.08.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.

7. Euchitonia stöhrii, n. sp. (Pl. , fig. 12).

Distance between the paired arms about four-fifths as large as their distance from the odd arm, which is one and a half times as long as the former. Arms about three times as long as broad, twice as broad in the distal half as in the proximal half, with rounded blunt ends. Patagium complete, with concave chamber-rows, enveloping the whole shell, also the ends of the arms.

Dimensions.—Radius of the paired arms 0.2, of the odd arm 0.25; basal breadth 0.03, distal breadth 0.06.

Habitat.—Fossil in the rocks of Barbados and of Nicobar Islands, Haeckel. Indian Ocean, Cocos Islands (Rabbe). Also in the Central Pacific, Station 267.

8. Euchitonia beckmannii, Haeckel.

Euchitonia beckmannii, Haeckel, 1862, Monogr. d. Radiol., p. 505, Taf. xxxi. fig. 1.

Distance between the paired arms scarcely half as large as their distance from the odd arm, which is somewhat larger. Each arm with six simple broad chambers (without radial septa), the terminal chambers semilunar, convex, blunt, four times as broad as the first (basal) chamber. Patagium incomplete, with convex chamber-rows, enveloping the arms with exception of the broad blunt terminal face.

Dimensions.—Radius of the paired arms 0.15, of the odd arm 0.18; basal breadth 0.02 to 0.03, terminal breadth 0.1 to 0.15.

Habitat.—Mediterranean (Messina), Haeckel, surface.

9. Euchitonia virchowii, Haeckel.

Euchitonia virchowii, Haeckel, 1862, Monogr. d. Radiol., p. 503, Taf. xxx. figs. 1-4.

Histiastrum fasciatum, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 842.

Distance between the paired arms about half as large as their distance from the odd arm, which is somewhat larger. Each arm with six broad chambers, bisected by a radial septum; the terminal chamber convex, blunt, twice as broad as the basal chamber. Patagium incomplete, with concave chamber-rows, enveloping the arms with exception of the broad blunt terminal face.

Dimensions.—Radius of the paired arms 0.15, of the odd arm 0.16; basal breadth 0.05, terminal breadth 0.1 to 0.12.

Habitat.—Mediterranean (Messina), Atlantic (Canary Islands).

Subgenus 2. Pteractis, Ehrenberg, 1872 (loc. cit.).

Definition.—Arms provided with radial spines at the distal end.

10. Euchitonia elegans, Haeckel.

Pteractis elegans, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 299, Taf. viii. fig. 3.

Distance between the paired arms half as large as their distance from the odd arm. This latter is straight, while both the former are concavely curved towards the middle line. Arms five times as long as broad, at the distal end pointed and armed with a short conical terminal spine. Patagium nearly complete, enveloping four-fifths of the arms, with four to five concave chamber-rows.

Dimensions.—Radius of the arms 0.2, breadth of them 0.03.

Habitat.—Tropical Pacific, Philippine Sea, depth 3300 fathoms (Ehrenberg).

11. Euchitonia carcinus, n. sp. (Pl. , fig. 10).

Distance between the paired arms scarcely one-fourth as great as their distance from the odd arm. This latter is straight, twice as long as the former, which are concavely curved towards the middle line. The odd arm is three times as broad at the distal end as at the narrow base. The end of each arm is furnished with a strong triangular radial spine and a group of smaller spines. Patagium incomplete, with two to three concave chamber-rows, enveloping only the basal half of the arms.

Dimensions.—Radius of the paired arms 0.15, breadth 0.03; radius of the odd arm 0.3, breadth on its base 0.02, on its distal end 0.07.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

12. Euchitonia acuta, Stöhr.

Euchitonia acuta, Stöhr, 1880, Palæontogr., vol. xxvi. p. 111, Taf. v. fig. 6.

Distance between the paired arms two-thirds as great as their distance from the odd arm. All three arms nearly of the same size and form, two and a half times as long as broad, nearly lanceolate, at their broadest part one and a half times as broad as at their base. Patagium complete, enveloping the whole triangular disk, with five to six concave chamber-rows. In the figure of Stöhr the ends of the arms are simply pointed, while I find in the same fossil form a short terminal conical spine.

Dimensions.—Radius of all three arms 0.14; breadth at the base 0.04, at the broadest part 0.06.

Habitat.—Fossil in Tertiary rocks of Sicily, Grotte (Stöhr), Caltanisetta (Haeckel).

13. Euchitonia ypsiloides, Haeckel.

Histiastrum ypsiloides, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 843.

Distance between the paired arms two-thirds as great as their distance from the odd arm, which is somewhat larger. Length of the arms equals five times the breadth of the narrow base, which is half that of the distal end; this latter is armed with three to five short conical spines. Patagium complete, with six to seven concave chamber-rows, enveloping the whole arms with the exception of the terminal spines. (Differs from Euchitonia mülleri almost solely by the possession of terminal spines.)

Dimensions.—Radius of the arms 0.18 to 0.2; breadth at the base 0.04, at the distal end 0.08.

Habitat.—Mediterranean (Messina), Atlantic (Canary Islands), surface.

14. Euchitonia echinata, n. sp. (Pl. , fig. 11).

Distance between paired arms three-fourths as great as their distance from the odd arm, which is somewhat larger. Arms one and a half times as long as broad, somewhat constricted in the middle part, armed at the rounded ends with numerous (thirty to forty) strong, conical spines. Patagium complete, with four or five rectilinear parallel chamber-rows, enveloping the whole of the arms with the exception of the spiny ends.

Dimensions.—Radius of the arms (without spines) 0.2, breadth 0.06 to 0.09.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

Genus 231. Chitonastrum, Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with three forked, chambered arms, without a patagium. (Arms and angles between them either equal or unequal.)

The genus Chitonastrum differs from its ancestral form, Dictyastrum, by the bifurcation of the distal ends of the arms. The few species of this genus are partly regular (like Dictyastrum), partly bilateral (like Rhopalastrum). If the number of species increases much, these two subgenera may be separated into two genera: Chitonastrella corresponding to the former, Chitonastromma to the latter.

Subgenus 1. Chitonastrella, Haeckel.

Definition.—All three arms of the same size and form, equidistant; fundamental form of the shell therefore an equilateral triangle.

1. Chitonastrum triglochin, n. sp.

All three arms equal and equidistant. Each arm has the form of an isosceles triangle, twice as high as broad; the truncated apex of the triangle is inserted into the large central disk, whilst its distal base (four times as broad) is divided by a deep incision (half as long as the arm). Each arm with ten to twelve joints, simple in its basal half, double in its distal half. Axes of the six branches straight. (Resembles Trigonastrum regulare, Pl. , fig. 16, but differs in the absence of a patagium.)

Dimensions.—Radius of each arm 0.24, greatest breadth 0.11, basal breadth 0.03.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

2. Chitonastrum bathybium, n. sp.

All three arms equal and equidistant, in the basal two-thirds simple, rectilinear, three times as long as broad, in the distal third forked, both branches equal, straight, blunt, half as broad as the basal part.

Dimensions.—Radius of each arm 0.18, basal breadth 0.04, breadth of the branches 0.02.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

Subgenus 2. Chitonastromma, Haeckel.

Definition.—One odd arm different in size or form from the two other arms, which are paired; distance between them different; fundamental form of the shell therefore a bilateral, isosceles triangle.

3. Chitonastrum jugatum, n. sp. (Pl. , fig. 14).

Dictyastrum jugatum, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. 14).

Arms very different; odd arm club-shaped, twice as long as broad, at the blunt distal end twice as broad as at the base; its axis is perpendicular to the common axis of both paired arms, which are only two-thirds as long, not so broad, and in the distal half divided into two branches; the anterior branch is straight, nearly horizontal, the posterior shorter and curved backwards.

Dimensions.—Radius of the odd arm 0.2, of the paired arms 0.15; distal breadth of the former 0.08, basal breadth 0.04; breadth of the paired arms 0.04.

Habitat.—South Atlantic, Station 325, surface.

4. Chitonastrum dicranoides, n. sp.

All three arms in the basal half simple, nearly square, in the distal half forked; branches straight, blunt. Odd arm twice as large as the paired arms; angle between the latter larger than the angles between them and the odd arm. (The form of the arms resembles Dicranastrum furcatum, Pl. , fig. 2.)

Dimensions.—Radius of the odd arm 0.24, of the paired arms 0.12; basal breadth 0.06.

Habitat.—North Atlantic, Station 353, surface.

5. Chitonastrum lyra, n. sp. (Pl. , fig. 15).

Dictyastrum lyra, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. 15).

All three arms forked and nearly of the same size, but different in form and position. The distance between the branches of the two paired arms is only one-fourth of the distance between them and the odd arm. Each arm in the basal two-thirds is simple, with eleven to twelve transverse septa, in the distal third forked, each branch with four to five transverse septa. The branches of each arm are curved convexly one to another, ending obtusely. The axis of the simple proximal part is straight in the odd arm, in the paired arms curved concavely towards the middle line. In the figured specimen, which I observed living in Portofino (in September 1880), the central chamber of the central disk and the first surrounding ring were filled with the nucleus of the cell; both external rings were filled (like all chambers of the arms) with pink oil-globules of the red central capsule. From the mantle, enveloping the shell, radiated innumerable fine pseudopodia (much too short in the figure), and between the two paired arms a long "sarcode-flagellum."

Dimensions.—Radius of each arm 0.16; greatest breadth of the odd arm 0.04; basal breadth of the paired arms 0.02; distance of both branches of each arm 0.08.

Habitat.—Mediterranean, Portofino, near Genoa, Haeckel.

Genus 232. Trigonastrum, n. gen.

Definition.—Porodiscida with three forked, chambered arms, connected by a patagium. (Arms and angles between them either equal or unequal.)

The genus Trigonastrum differs from the preceding Chitonastrum, its ancestral form, in the development of a patagium between the arms. It bears therefore to the latter the same relation that Euchitonia does to Rhopalastrum.

Subgenus 1. Trigonastrella, Haeckel.

Definition.—All three arms of the same size and form, equidistant; fundamental form of the shell therefore a regular, equilateral triangle.

1. Trigonastrum regulare, n. sp. (Pl. , fig. 16).

Chitonastrum regulare, Haeckel, 1881, Prodromus et Atlas (pl. xliii. fig. 16).

All three arms equal and equidistant. Each arm has the form of an isosceles triangle, twice as high as broad, the truncated apex of which is inserted into the large circular central disk, whilst its distal base (four times as broad) is divided by a deep incision (half as long as the arm). Each arm with ten to twelve joints. Patagium between the arms nearly complete, spongy. (Differs from Chitonastrum triglochin mainly in the possession of a patagium.)

Dimensions.—Radius of each arm 0.24, greatest breadth 0.11, basal breadth 0.03; length of the sides of the regular triangle 0.45.

Habitat.—Pacific, central area, Station 274, surface.

Subgenus 2. Trigonastromma, Haeckel.

Definition.—One odd arm different in form or size from the other two arms, which are paired; distance between them different; fundamental form of the shell therefore an isosceles triangle.

2. Trigonastrum krohnii, Haeckel.

Euchitonia krohnii, Haeckel, 1862, Monogr. d. Radiol., p. 507.

All three arms different; distance between the two paired arms smaller than their distance from the odd arm. Odd arm with six joints. Each paired arm with seven joints, increasing in breadth towards the distal end. Odd arm and one paired arm forked at the end, the other paired arm simple. Patagium nearly complete. (The asymmetry in this form may perhaps be an individual anomaly, as also in Myelastrum anomalum, Pl. , fig. 9.)

Dimensions.—Radius of the arms about 0.13 to 0.16, breadth 0.05 to 0.08.

Habitat.—North Atlantic, Funchal, Madeira, Krohn, surface.

3. Trigonastrum gegenbauri, Haeckel.

Euchitonia gegenbauri, Haeckel, 1862, Monogr. d. Radiol., p. 506, Taf. xxxi. figs. 2, 3.

Arms different; distance between the paired arms larger than their distance from the odd arm, which is one-third shorter. Odd arm egg-shaped, simple, with seven joints, undivided. Both paired arms equal, with ten joints, in the distal third forked. Patagium nearly complete.

Dimensions.—Radius of the odd arm 0.14, greatest breadth 0.08; radius of the paired arms 0.2.

Habitat.—Mediterranean (Messina), Haeckel, surface.

Genus 233. Stauralastrum, n. gen.

Definition.—Porodiscida with four simple, undivided, chambered arms, without a patagium; quadrangular shell a regular cross, with four equal arms placed at right angles.

The genus Stauralastrum is the most simple form of the Tessarastrida, or of those Porodiscida in which the margin of the central disk is armed with four chambered arms. In Stauralastrum these four arms are quite simple and equal, without a patagium, separated by four right angles, so that the whole shell represents a regular rectangular cross. If we connect the distal points of the arms by lines, we get a complete square. (In my Prodromus, 1881, the species of this genus were united with Hagiastrum, which genus I now retain for the simple bilateral Tessarastrida.)

Subgenus 1. Stauralastrella, Haeckel.

Definition.—Ends of the arms blunt, without terminal spines.

1. Stauralastrum cruciforme, n. sp. (Pl. , fig. 6).

Arms very thin, nearly linear, four to five times as long as broad, of equal breadth at the base and at the truncated distal end; their breadth equals one-third of the radius of the central disk. Edges of the arms parallel.

Dimensions.—Radius of each arm 0.8, breadth 0.016.

Habitat.—South Pacific, Station 293, surface.

2. Stauralastrum lanceolatum, n. sp.

Arms lanceolate, three times as long as broad, in their middle part three times as broad as at both ends; their greatest breadth nearly equals the diameter of the central disk. (The arms have the same form as in Euchitonia lanceolata, Pl. , fig. 9.) Edges of the arms convex.

Dimensions.—Radius of each arm 0.3, greatest breadth (in the middle part) 0.08.

Habitat.—Pacific, central area, Station 273, depth 2350 fathoms.

3. Stauralastrum ordo, n. sp.

Arms trapezoid, about as long as broad, twice as broad at their truncated distal end as at the base; their basal breadth equals the radius of the central disk, which exhibits two to three rings. (The arms have nearly the same form as those in Hagiastrum mosis, Pl. , fig. 3.) Edges of the arms rectilinear, divergent towards the ends.

Dimensions.—Radius of each arm 0.12, basal breadth 0.04, distal breadth 0.08.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

4. Stauralastrum clavigerum, n. sp.

Arms twice as long as broad, in their distal half lenticular, nearly circular, twice as broad as in their square proximal half; their distal breadth equals the diameter of the central disk, which exhibits three to four rings. Edges of the arms concave.

Dimensions.—Radius of each arm 0.2, basal breadth 0.04, distal breadth 0.08.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

5. Stauralastrum dilatatum, n. sp.

Arms of nearly equal length and breadth, at their convex distal end three times as broad as at their narrow base; their distal breadth three times as large as the radius of the central disk, which exhibits three to four rings. (Resembles Histiastrum quadrigatum, Pl. , fig. 3, but has no patagium.) Edges of the arms concave.

Dimensions.—Radius of each arm 0.15, basal breadth 0.04, terminal breadth 0.12.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

Subgenus 2. Stauralastromma, Haeckel.

Definition.—Ends of the arms with one or more terminal spines.

6. Stauralastrum rhopalophorum, n. sp. (Pl. , fig. 1).

Hagiastrum rhopalophorum, Haeckel, 1881, Prodromus, p. 460.

Arms cylindrical, eight times as long as broad at their base, at their distal end club-shaped, three times as broad as at their base; their distal breadth twice as large as the diameter of the central disk, which exhibits two to three rings. Surface thorny, with larger spines towards the end, and one radial, very strong, angular terminal spine. Edges of the arms parallel.

Dimensions.—Radius of each arm (without terminal spine) 0.32, basal breadth 0.03, terminal breadth 0.1.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

7. Stauralastrum antiquum, n. sp.

Rhopalastrum sp. Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 5.

Arms six times as long as broad at their base, in their distal half nearly spherical, three times as broad as in their cylindrical basal half; their distal breadth nearly equals the diameter of the central disk which exhibits three to four rings. On the end of each arm one strong, angular, terminal spine. (Differs from the preceding species by larger central disk and stouter arms, also by less developed spines.) Edges of the arms parallel.

Dimensions.—Radius of each arm 0.25, basal breadth 0.04, terminal breadth 0.12.

Habitat.—Fossil in the Barbados rocks; and living in the depths of the Central Pacific, Station 266, depth 2750 fathoms.

8. Stauralastrum staurolonche, n. sp.

Arms four times as long as broad at their base, gradually increasing towards their truncated end, which is one and a half times as broad as their base; their distal breadth equals the radius of the central disk, which exhibits four to five rings. At the end of each arm is a very strong conical terminal spine. (Resembles Histiastrum quaternarium, Abhandl. k. Akad. Wiss. Berlin, 1875, Taf. xxiv. fig. 3, but has no patagium.) Edges of the arms rectilinear, divergent.

Dimensions.—Radius of each arm 0.25, basal breadth 0.045, distal breadth 0.07.

Habitat.—Fossil in the Barbados rocks; and living in the depth of the Equatorial Atlantic, Station 348, depth (2450) fathoms.

9. Stauralastrum horridum, n. sp.

Arms three times as long as broad at their base, gradually increasing towards their rounded end, which is twice as broad as their base, their distal breadth equals the diameter of the central disk, which exhibits four to five rings. Surface thorny, at the distal end of each arm is a group of twenty to twenty-five smaller and five to six larger, straight, conical spines. Edges of the arms rectilinear, divergent.

Dimensions.—Radius of each arm 0.15, basal breadth 0.05, distal breadth 0.1.

Habitat.—Pacific, central area, Station 270, depth 2925 fathoms.

Genus 234. Hagiastrum, Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with four simple, undivided, chambered arms, without a patagium; quadrangular shell bilateral, two opposite arms of the main axis (or principal arms) different from the two others (or lateral arms).

The genus Hagiastrum, as here defined, was formerly united by me with the foregoing Stauralastrum, but differs from it by the bilateral or symmetrical form. Whilst in the latter all four arms and the four angles between them are equal, they are here differentiated into pairs.

Subgenus 1. Hagiastrella, Haeckel.

Definition.—Both longitudinal arms of equal size and form.

1. Hagiastrum buddhae, n. sp. (Pl. , fig. 5).

Cross rectangular. Both longitudinal arms of equal size, twice as long as the transverse arms; all arms smooth, club-shaped, twice as broad at their globose distal part as at their base, each with three large conical terminal spines.

Dimensions.—Radius of the principal arms 0.4, of the lateral arms 0.2; basal breadth 0.06, distal breadth 0.12.

Habitat.—Indian Ocean, Belligemma, Ceylon, surface, Haeckel.

2. Hagiastrum bramae, n. sp.

Cross rectangular. Both longitudinal arms of equal size, one and a half times as long as the transverse arms; all arms thorny, club-shaped, at their pear-shaped distal part three times as broad as at their base, provided with numerous conical spines, one larger terminal spine at their distal point. (Resembles Stauralastrum rhopalophorum, Pl. , fig. 1, but is distinguished by the different size of the arm-pairs, and by the stronger spines.)

Dimensions.—Radius of the principal arms 0.3, of the lateral arms 0.2; basal breadth 0.04, distal breadth 0.12.

Habitat.—Indian Ocean, off Maldive Islands, surface, Haeckel.

Subgenus 2. Hagiastromma, Haeckel.

Definition.—The two longitudinal arms different in size or form.

3. Hagiastrum mosis, n. sp. (Pl. , fig. 3).

Cross rectangular. All four arms nearly isosceles, triangular, at their narrow base half as broad as at their truncated, concavely fluted, distal end. The posterior principal arm with twelve to thirteen joints, twice as long as the anterior arm, which has six to seven joints and is one and a half times as long as the two lateral arms (with four to five joints).

Dimensions.—Radius of the posterior arm 0.3, of the anterior 0.15, of the lateral arms 0.1; basal breadth 0.05, terminal breadth 0.1.

Habitat.—Mediterranean (Smyrna), surface, Haeckel.

4. Hagiastrum mohammedis, n. sp.

Cross with unequal angles, the anterior little smaller than the posterior. All four arms club-shaped, thorny, three times as broad at their globose distal end as at their narrow base, and furnished with ten to twelve conical spines. Posterior principal arm twice as long as the anterior, and four times as long as the rudimentary lateral arms.

Dimensions.—Radius of the posterior arm 0.4, of the anterior 0.2, of the lateral arms 0.1; basal breadth 0.02 to 0.03, distal breadth 0.06 to 0.1.

Habitat.—Philippine Sea, Samboangan, Station 200, surface.

5. Hagiastrum christi, n. sp.

Cross with unequal angles, the anterior somewhat smaller than the posterior. All four arms of similar form, lanceolate, in their middle twice as broad as at either obtuse end. The posterior principal arm with twelve joints, one and a half times as long as the anterior (with nine joints) and twice as long as the two lateral arms (each with six joints). The form and structure of the arms in this species are nearly the same as in Tessarastrum straussi (Pl. , fig. 8); but the arms are broader in the middle, and are not connected by a patagium.

Dimensions.—Radius of the principal posterior arm 0.2, of the anterior 0.15, of each lateral arm 0.1; greatest breadth (in the width) 0.01, basal breadth 0.03.

Habitat.—North Atlantic, Færöe Channel, Gulf Stream, surface, John Murray.

Genus 235. Histiastrum, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Porodiscida with four simple, undivided, chambered arms, connected by a patagium; square shell a regular cross, with four equal arms and four right angles between them.

The genus Histiastrum, quite insufficiently characterised by Ehrenberg (1847), was afterwards (1875) illustrated by the figures of two different fossil species. One of these, Histiastrum ternarium, with three arms, belongs to Hymeniastrum; the other, Histiastrum quaternarium, is here retained as the true, typical representative species of the genus. It differs from its ancestral form Stauralastrum, by the possession of a patagium, from Tessarastrum by the regular square form of the shell.

Subgenus 1. Histiastrella, Haeckel.

Definition.—Distal ends of the arms blunt, without terminal spines.

1. Histiastrum quadrigatum, n. sp. (Pl. , fig. 3).

Arms at their distal end nearly as broad as long, and four times as broad as at their narrow base; their lateral edges concave, their terminal edge convex, without spines. Each arm is divided by seven to eight convex transverse septa into eight to nine simple, broad chambers. Central disk with three to four rings, about as broad as the fifth chamber. Patagium complete, connecting all the lateral edges of the arms.

Dimensions.—Radius of each arm 0.15, basal breadth 0.03, terminal breadth 0.12.

Habitat.—Equatorial Atlantic, Station 347, surface.

2. Histiastrum excisum, n. sp.

Arms four times as long as broad at their base, and twice as broad at their rounded blunt distal end as at their base; their lateral edges rectilinear, divergent. Central disk with three to four rings, somewhat broader than their distal end. Patagium incomplete, connecting only the basal half of the arms, with three to four concave chamber-rows, on the margin concave. (May be regarded as Euchitonia mülleri, with four arms.)

Dimensions.—Radius of each arm 0.2, basal breadth 0.05, distal breadth 0.1.

Habitat.—Atlantic, surface, Canary Islands.

3. Histiastrum velatum, n. sp. (Pl. , fig. 4).

Dictyastrum velatum, Haeckel, 1879, Atlas (pl. xlvi. fig. 4).

Arms pear-shaped, rapidly increasing from their narrow base, nearly circular, little longer than broad; each with eight to nine transverse chamber-rows; their lateral edges at their base concave, at their end circular. Central disk with three to four rings, somewhat smaller than one arm. Patagium complete, with six to seven radial beams, filling out perfectly the intervals between the arms. A peculiar girdle of finer network and equal breadth surrounds the whole equatorial periphery of the disk, and gives it the appearance of a square with rounded corners.

Dimensions.—Radius of each arm 0.2, basal breadth 0.03, distal breadth 0.12.

Habitat.—South Atlantic, Station 330, surface.

Subgenus 2. Histiastromma, Haeckel.

Definition.—Distal ends of the arms spiny, furnished with one or more terminal spines.

4. Histiastrum quaternarium, Ehrenberg.

Histiastrum quaternarium, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 74, Taf. xxiv. figs. 3, 4.

Arms six times as long as broad at their base, with rectilinear, little divergent edges; at their truncated distal end a little broader, with one single, very strong, conical, terminal spine. Central disk with four to five rings, somewhat broader than the arm. Patagium incomplete, enveloping only the basal half of the arms.

Dimensions.—Radius of each arm 0.18, basal breadth 0.03, distal breadth 0.05.

Habitat.—Fossil in the rocks of Barbados.

5. Histiastrum gladiatum, n. sp.

Astromma sp., Bury, 1862, Polycystins of Barbados, pl. v. fig. 1.

Arms triangular, eight times as long as broad at their base; at their distal end three times as broad as at their base, with rectilinear, divergent edges; their truncated end with a large conical, terminal spine. Central disk with four to five rings, broader than the arms. Patagium incomplete, enveloping only the basal half of the arms.

Dimensions.—Radius of each arm 0.12, basal breadth 0.013, distal breadth 0.04.

Habitat.—Fossil in the rocks of Barbados; and living in the depth of the Central Pacific, Station 268, depth 2900 fathoms.

6. Histiastrum boseanum, n. sp. (Pl. , fig. 1).

Arms linear, twelve times as long as broad at their base (at their distal end twice as broad as at their base), with rectilinear, parallel edges. The club-shaped end thickened, dentate, with two lateral rows of strong teeth in the equatorial plane, and with one very stout, angular, terminal spine. Central disk with two to three rings, broader than the arms. Patagium incomplete, with four to five concave chamber-rows, enveloping only the basal half of the arms. I call this splendid species in honour of Dr. Graf Bose, the great friend of nature and patron of the University of Jena.

Dimensions.—Radius of each arm 0.25, basal breadth 0.02, distal breadth 0.05.

Habitat.—Indian Ocean, Madagascar, Rabbe.

7. Histiastrum coronatum, n. sp.

Stephanastrum sp., Bury, 1862, Polycystins of Barbados, pl. iv. fig. 1.

Arms linear, eight times as long as broad, with rectilinear parallel edges; the thickened, nearly spherical, distal end three times as broad, with five strong conical spines, one middle (perradial) larger and two smaller on each side of it. Central disk with two to three rings, of the same breadth as the terminal knot of the arms. Patagium incomplete, square, enveloping the arms, with the exception of the knot.

Dimensions.—Radius of each arm 0.16, basal breadth 0.02, terminal breadth 0.06.

Habitat.—Fossil in the rocks of Barbados.

8. Histiastrum circulare, n. sp.

Stephanastrum sp., Bury, 1862, Polycystins of Barbados, pl. xxiii. fig. 1.

Arms linear in their inner half, egg-shaped and three times as broad in their outer half, with ten to twelve strong terminal spines, the middle (perradial) larger, in all three times as long as broad. Central disk with three to four rings, broader than their distal knobs. Patagium nearly complete, circular, enveloping the whole arms, with exception of the outermost end.

Dimensions.—Radius of each arm 0.22, basal breadth 0.02, terminal breadth 0.06.

Habitat.—Fossil in the rocks of Barbados; and living in the depths of the Central Pacific, Station 268, depth 2900 fathoms.

9. Histiastrum pentadiscus, n. sp. (Pl. , fig. 2).

Arms in their inner half linear, twice as long as broad, in their outer half circular, three times as broad, with the same structure as the central disk, exhibiting three concentric rings around one central chamber. Patagium complete, spongy, with radiating beams, enveloping the whole disk, with the exception of the outermost end of the arms, which is armed with twelve to sixteen strong conical spines, the middle (perradial) spine much larger.

Dimensions.—Radius of each arm (without terminal spine) 0.18, basal breadth 0.025, terminal breadth 0.08.

Habitat.—South Atlantic, Station 333, surface.

Genus 236. Tessarastrum, n. gen.

Definition.—Porodiscida with four simple, undivided, chambered arms, connected by a patagium; quadrangular shell bilateral, two opposite arms of the main axis (or principal arms) different from the two others (or lateral arms).

The genus Tessarastrum, formerly united by me with Histiastrum, differs from the latter in its bilateral or symmetrical form, and bears therefore the same relation to it that Hagiastrum does to Stauralastrum.

Subgenus 1. Tessarastrella, Haeckel.

Definition.—Both longitudinal arms of equal size and form.

1. Tessarastrum straussii, n. sp. (Pl. , fig. 8).

Histiastrum straussii, Haeckel, 1881, Prodromus et Atlas (pl. xlv. fig. 8).

Cross not rectangular. Both principal arms of equal size and form, four times as long as broad, and twice as long as the broader lateral arms; the former with ten to eleven, the latter with five to six joints, separated by convex transverse septa. Distal ends of the arms blunt. Axes of the smaller arms not perpendicular to that of the larger arms; therefore the anterior angles between them smaller than the posterior angles. Patagium between the arms incomplete. I call this remarkable species after the great German philosopher David Strauss.

Dimensions.—Radius of the principal arms 0.24, of the lateral arms 0.12; greatest breadth (in the middle) of the former 0.05, of the latter 0.06.

Habitat.—North Pacific, Hyalonema-ground, March 5, 1875.

2. Tessarastrum spinozæ, n. sp.

Cross rectangular. Both principal arms of equal size and form, ten times as long as broad, and twice as long as the lateral arms, which are only five times as long as broad. All arms linear, at their distal end club-shaped, and armed with twenty to thirty very strong angular spines. Patagium incomplete, enveloping only the basal half of the arms. (Resembles Histiastrum boseanum, Pl. , fig. 1, but differs in the broader arms and the unequal size of both pairs.) I call this species after the great monistic philosopher Benedictus Spinoza.

Dimensions.—Radius of the principal arms 0.3, of the lateral arms 0.16; basal breadth 0.025, distal breadth 0.05.

Habitat.—South Atlantic, Station 333, surface.

3. Tessarastrum brunonis, n. sp. (Pl. , fig. 9).

Histiastrum brunonis, Haeckel, 1881, Prodromus et Atlas (pl. xlv. fig. 9).

Cross rectangular. Both principal arms of equal size and form, three times as long as broad, each with ten joints, three times as long as the lateral arms, which are nearly square, with four joints. All arms rounded, at their truncated end little broader than at their base. No spines. Patagium complete, envelops the whole shell, and is composed of two parallel lattice-lamellæ on each side of the flat disk, which are connected by very fine perpendicular bars. This is shown clearly in fig. 9, Pl. , where the disk is seen from the edge. I call this species after the great Italian philosopher Giordano Bruno.

Dimensions.—Radius of the principal arms 0.22, of the lateral arms 0.12; basal breadth 0.04, distal breadth 0.05.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

Subgenus 2. Tessarastromma, Haeckel.

Definition.—The two principal arms of different size or form.

4. Tessarastrum democriti, n. sp. (Pl. , fig. 7).

Histiastrum democriti, Haeckel, 1881, Prodromus et Atlas (pl. xlv. fig. 7).

Cross not rectangular; the two anterior angles smaller than the two posterior. All four arms club-shaped, twice as broad at their rounded obtuse distal end as at their base, of unequal length. Posterior principal arm one and a fourth times as long as the posterior, and one and two-thirds as long as the lateral arms. Patagium incomplete, enveloping only the basal half of the arms. I call this species after the great Greek philosopher Democritus.

Dimensions.—Radius of the posterior arm 0.3, of the anterior 0.25, of each lateral arm 0.22; basal breadth 0.05, distal breadth 0.1.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

Genus 237. Stephanastrum, Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Porodiscida with four simple, undivided, chambered arms, connected on the distal ends by a spongy, square or rhomboidal, patagial girdle (or a patagium with four large, interbrachial openings). Shell either regular or bilateral (with equal or unequal arms).

The genus Stephanastrum, founded (1847) by Ehrenberg for the very peculiar Stephanastrum rhombus, differs from the nearly allied foregoing genera in the imperfect development of the peculiar patagium, connecting only the distal ends of the four arms, while it is absent at their base. Two new species, different from Stephanastrum rhombus by the regular square form, were found in the Challenger collection.

Subgenus 1. Stephanastrella, Haeckel.

Definition.—All four arms of the cross have the same size.

1. Stephanastrum quadratum, n. sp. (Pl. , fig. 5).

All four arms of the same size, six times as long as broad at their base, ending with a strong, short, four-sided pyramidal spine. In the outer half of each arm are two opposite lateral spongy wings, which form an equilateral triangle, and from union of the bases of the four triangles arises the peculiar patagium, which forms a square with four large interbrachial openings.

Dimensions.—Radius of each arm 0.25, basal breadth 0.035; length of the sides of the square patagium 0.3.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

2. Stephanastrum capitatum, n. sp. (Pl. , fig. 1).

All four arms of the same size, five times as long as broad at their base, at their distal end with a spongy, nearly spherical capitulum of twice their breadth, provided with a very strong, angular, pyramidal, terminal spine (half as long as the arm). All four arms connected by a square patagium, arising immediately below the capitula, and perforated by four large interbrachial openings.

Dimensions.—Radius of each arm (without the terminal spine) 0.25, basal breadth 0.05; length of the sides of the square patagium 0.3.

Habitat.—Pacific, central area. Station 265, depth 2900 fathoms.

Subgenus 2. Stephanastromma, Haeckel.

Definition.—Two opposite arms of the cross larger than the two others.

3. Stephanastrum rhombus, Ehrenberg.

Stephanastrum rhombus, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 33; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, Taf. xxv. fig. 1.

Two arms of the longitudinal axis one and a third times as long as two arms of the transverse axis. All four arms linear, about eight times as long as broad, at their distal end somewhat thickened, club-shaped, with a pyramidal terminal spine. The ends of the arms are connected by a riband-shaped, straight, spongy patagium of the same breadth as the arms. Between the rhomboidal patagium and the arms remain four large rectangular triangles as interbrachial openings.

Dimensions.—Radius of the longer arms 0.2, of the shorter 0.15; basal breadth 0.02; length of the sides of the rhombic patagium 0.25.

Habitat.—Fossil in the rocks of Barbados.

Genus 238. Dicranastrum, Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with four forked, spongy, or chambered arms, without a patagium; shell regular (not bilateral), with four equal arms crossed at right angles.

The genus Dicranastrum comprises a number of very remarkable, hitherto unknown, Euchitonida, which are rather common in the Pacific (mainly on the surface), and characterised by the bifurcation of the cross-arms of the regular square shell. It bears therefore to its probable ancestral form, Stauralastrum, the same relation that in the triradiate Euchitonida Chitonastrum does to Dictyastrum. The arms are commonly of very delicate structure, more or less spongy.

Subgenus 1. Dicranaster, Haeckel.

Definition.—Each cross-arm with two simple branches.

1. Dicranastrum furcatum, n. sp. (Pl. , fig. 2).

Arms simply forked, three times as long as broad at their base, with eight blunt ends of the fork-branches. The simple proximal half of each arm about the same size as each branch of the dichotomous distal part, twice as long as broad. Edges of the arms ragged.

Dimensions.—Radius of each arm 0.38, basal breadth 0.12; breadth of the forked part 0.3.

Habitat.—Pacific, central area, Station 271, surface.

2. Dicranastrum dichotomum, n. sp.

Arms simply forked, four times as long as broad at their base; each arm with two blunt branches. The simple proximal part of each arm is three times as long and twice as broad as each branch of the dichotomous distal part. Ends of the arms blunt, truncated.

Dimensions.—Radius of each arm 0.35, basal breadth 0.08; breadth of the forked part 0.2.

Habitat.—South Pacific, Station 281, surface.

3. Dicranastrum cornutum, n. sp. (Pl. , fig. 2).

Hagiastrum cornutum, Haeckel, 1879, Atlas (pl. xlv. fig. 2).

Four arms simply forked, four times as long as broad; each arm with two triangular diverging branches ending in strong conical spines. The simple basal part of each arm about of the same length as each branch of the distal part, twice as long as broad. Distance between the terminal spines of each arm nearly as great as its length.

Dimensions.—Radius of the arm 0.24, basal breadth 0.05; breadth across the bifurcation 0.12.

Habitat.—South Atlantic, Station 325, surface.

4. Dicranastrum antilope, n. sp.

Four arms simply forked, three times as long as broad; each arm with two lanceolate diverging branches, ending in strong angular spines. The simple basal part of each arm is twice as long as each branch of the distal part. Distance of the two terminal spines of each arm scarcely half as great as its length.

Dimensions.—Radius of the arm 0.32, basal breadth 0.11; breadth of the branches 0.07.

Habitat.—Tropical Atlantic (off Ascension), Station 342, surface.

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

Definition.—Each cross arm with three terminal branches, one middle (perradial) and two lateral (adradial) branches.

5. Dicranastrum wyvillei, n. sp. (Pl. , fig. 3).

Tricranastrum wyvillei, Haeckel, 1879, Natürl. Schöpfungsgesch., p. 705, Taf. xvi. fig. 5.

Arms trifid, one and a half times as long as broad; each arm with three blunt terminal branches of equal size. The simple basal part of each arm twice as long as the trifid distal part. (The central capsule depicted in fig. 3, Pl. , has the same form as the skeleton, and is only a little smaller.)

Dimensions.—Radius of the arm 0.4, basal breadth 0.12, greatest breadth (in the distal part) 0.24.

Habitat.—Pacific, central area, Station 271, surface.

6. Dicranastrum tricuspis, n. sp.

Arms trifid, twice as long as broad; each arm with three pointed terminal branches, ending in strong conical spines, the middle branch somewhat larger than the other two. The simple basal part of each arm three times as long as the trifid distal part.

Dimensions.—Radius of the arm 0.3, basal breadth 0.06, greatest breadth (in their distal part) 0.15.

Habitat.—North Pacific, Station 244, surface.

7. Dicranastrum trifarium, n. sp.

Arms trifid, three times as long as broad at their base; each arm with three pointed terminal branches, ending in strong sulcate spines; the middle branch twice as large as the two others. The simple basal part of each arm two and a half times as long as the trifid distal part.

Dimensions.—Radius of the arm 0.35, basal breadth 0.03, greatest breadth (in the distal part) 0.05.

Habitat.—South Pacific, Station 298, surface.

Subgenus 3. Tetracranastrum, Haeckel.

Definition.—Each cross-arm with four terminal branches, the two fork-branches being again bifurcated.

8. Dicranastrum bifurcatum, n. sp. (Pl. , figs. 1, 1a).

Arms doubly forked or quadripartite, six times as long as broad at their base; each arm in its proximal half simple, three times as long as broad; in its distal half doubly forked; the secondary branches with blunt, roundish ends, nearly as large as the primary branches. Central disk (fig. 1a) with three concentric rings around the central chamber; from its periphery radiate thin radial beams in the spongy framework of the delicate arms. The central capsule has the same form as the skeleton, and is only a little smaller.

Dimensions.—Radius of the arm 0.45, basal breadth 0.08; breadth of the terminal branches 0.03.

Habitat.—North Pacific, east of Japan, Station 241, surface.

Genus 239. Myelastrum, Haeckel, 1881, Prodromus, p. 460.

Definition.—Porodiscida with four forked, spongy, or chambered arms, without a patagium; shell bilateral, with paired different arms; two equal anterior arms of different shape from the two equal posterior arms.

The genus Myelastrum differs from the foregoing Dicranastrum, the ancestral form, by the twofold differentiation of the four arms. Whilst in the latter all four arms are equal, separated by equal angles, here the two anterior arms are constantly different from the two posterior. The lateral angles between the two arm-pairs are equal, while the posterior and the anterior angle (between the two arms of each pair) are more or less different. The shell assumes, therefore, a very characteristic bilateral form, similar to the "quadricorn cross" of the grey central substance in the transverse section of the human medulla spinalis. Though the spongy shell is commonly a most delicate and thin disk it nevertheless reaches unusual dimensions, its diameter in some species being more than a millimetre.

Subgenus 1. Myelastrella, Haeckel.

Definition.—Posterior arms simple, undivided; anterior arms lobated or cleft, with one or more incisions at the distal end.

1. Myelastrum medullare, n. sp. (Pl. , fig. 13).

Anterior arms bifid, nearly square, with a shallow incision at their broad truncated end. Posterior arms somewhat smaller, nearly triangular, with simple blunt ends. Sagittal constriction three-fourths as large as the transverse one. Surface smooth.

Dimensions.—Radius of the anterior arms 0.36, of the posterior 0.3; longitudinal constriction 0.24, transverse 0.36.

Habitat.—Pacific, central area, Station 271, surface.

2. Myelastrum spinale, n. sp.

Anterior arms bifid, twice as long as broad, with a deep incision at their truncated end. Posterior arms slender, half as large, with simple blunt ends. Sagittal constriction one and a half times as large as the transverse. Surface spiny.

Dimensions.—Radius of the anterior arms 0.4, of the posterior 0.2; longitudinal constriction 0.3, transverse 0.2.

Habitat.—North Pacific, Station 248, surface.

3. Myelastrum heteropterum, n. sp. (Pl. , fig. 8).

Anterior arms trifid, about as long as broad, with two incisions at their broad truncated end. Posterior arms about half as large, simple, with rounded blunt ends. Sagittal constriction two-thirds as large as the transverse. Surface bristly.

Dimensions.—Radius of the anterior arms 0.65, of the posterior 0.035; longitudinal constriction 0.4, transverse 0.6.

Habitat.—South Pacific, Station 291, surface.

Subgenus 2. Myelastromma, Haeckel.

Definition.—All four arms (posterior as well as anterior) lobated or cleft.

4. Myelastrum octocorne, n. sp. (Pl. , fig. 12).

All four arms with a deep incision in their distal half; anterior arms broader, but shorter than the posterior; in the anterior arms the two lobes are of the same size, in the posterior arms the median lobe is longer than the lateral lobe. Sagittal constriction little smaller than the transverse. Surface of the disk rough.

Dimensions.—Radius of the anterior arms 0.45, of the posterior 0.62; longitudinal constriction 0.25, transverse 0.3.

Habitat.—Pacific, central area, Station 271, surface.

5. Myelastrum farfalla, n. sp. (Pl. , fig. 10).

All four arms with a shallow incision at their distal end. Anterior arms broader, but shorter than the posterior; in each arm the anterior lobe is shorter than the posterior. Sagittal constriction smaller than the transverse. Surface smooth.

Dimensions.—Radius of the anterior arms 0.4, of the posterior 0.6; longitudinal constriction 0.5, transversal stricture 0.6.

Habitat.—Pacific, central area, Station 274, surface.

6. Myelastrum papilio, n. sp. (Pl. , fig. 6).

All four arms with a shallow incision at their distal end. Anterior arms triangular, of the same breadth, but of the double length of the square posterior arms. Sagittal and transverse constrictions of the same length. Surface ciliated. (Resembles a butterfly.)

Dimensions.—Radius of the anterior arms 0.7, of the posterior 0.4; longitudinal and transverse constrictions 0.4.

Habitat.—North Pacific, near Japan, Station 241, surface.

7. Myelastrum decaceros, n. sp. (Pl. , fig. 7).

Anterior arms bifid, with one shallow incision at their distal end. Posterior arms of the same length, but much broader, trifid, with two incisions (one larger and one smaller). Sagittal and transverse constrictions of the same length. Surface spiny.

Dimensions.—Radius of all four arms 0.4; longitudinal and transverse constrictions 0.35.

Habitat.—Pacific, central area, Station 272, surface.

8. Myelastrum dodecaceros, n. sp. (Pl. , figs. 11, 11a).

Anterior arms trifid, with two shallow incisions at their distal end. Posterior arms about one-third larger, also trifid, with one deeper anterior and one shallower posterior incision. Sagittal constriction much longer than the transverse. Surface ciliated, covered with numerous thin and long radial bristles (fig. 11a).

Dimensions.—Radius of the anterior arms 0.5, of the posterior 0.7; longitudinal constriction 0.5, transverse 0.35.

Habitat.—Pacific, central area, Station 270, surface.

9. Myelastrum ciliatum, n. sp.

Anterior arms trifid, with two shallow incisions. Posterior arms somewhat smaller, also trifid, with two deeper incisions. Sagittal constriction a little larger than the transverse. Margin of the disk ciliated, with radial bristle-shaped spines, as prolongations of the inner radial beams, arising from the central disk.

Dimensions.—Radius of the anterior arms 0.6, of the posterior 0.5; longitudinal constriction 0.4, transverse 0.35.

Habitat.—South Pacific, Station 288, surface.

10. Myelastrum lobatum, n. sp.

Anterior arms somewhat broader but shorter than the posterior arms. Each arm four-lobed, with three terminal shallow incisions of nearly equal size. Sagittal constriction smaller than the transverse. Surface of the disk bristly.

Dimensions.—Radius of the anterior arms 0.4, of the posterior 0.5; longitudinal constriction 0.3, transverse 0.35.

Habitat.—North Pacific, Station 253, surface.

11. Myelastrum rotula, n. sp.

Anterior arms little broader than the posterior, but of the same length. Each arm four-lobed, with three terminal deep incisions of equal size. Sagittal and transverse constrictions equal. The whole disk nearly circular, resembles a wheel with sixteen spokes. Surface smooth.

Dimensions.—Radius of all four arms 0.5; longitudinal and transverse constrictions 0.3.

Habitat.—Pacific, central area, Station 274, surface.

12. Myelastrum giganteum, n. sp.

Anterior arms somewhat broader and shorter than the posterior. Each arm four-lobed, with three shallow terminal incisions, the middle incision twice as deep as the two laterals. Sagittal constriction a little larger than the transverse. Margin ciliated, with radial bristle-shaped spines as prolongations of the inner radial beams, proceeding from the central disk (as in Myelastrum dodecaceros, Pl. , figs. 11, 11a).

Dimensions.—Radius of the anterior arms 0.6, of the posterior 0.8; longitudinal constriction 0.6, transverse 0.5.

Habitat.—Pacific, central area, Station 271, surface.

13. Myelastrum anomalum, n. sp. (Pl. , fig. 9).

All four arms of different size and form; anterior arms broader, posterior longer; one anterior arm trifid, the three other arms bifid; length of the branches unequal; all four angles between the arms unequal. (This anomalous form, seen only once, may be an individual abnormality.)

Dimensions.—Radius of the arms 0.4 to 0.7; constrictions 0.3.

Habitat.—North Pacific, Station 237, surface.

Genus 240. Pentalastrum, Haeckel, 1881, Prodromus, p. 461.

Definition.—Porodiscida with five simple, undivided, chambered arms, without a patagium.

The genus Pentalastrum opens the small series of Euchitonida, in which the shell is not provided with three or four arms, as usual, but with five. All forms of this little group are rare. Some species resemble in their external form and in the articulation of their arms certain forms of Asterida. In Pentalastrum, the most simple genus, the five arms are simple, not forked, and without a patagium. It can be derived from Dictyastrum or Stauralastrum by increase of the number of arms.

Subgenus 1. Pentalastrella, Haeckel.

Definition.—All five arms equal, with equal angles between them. Shell a regular pentagon.

1. Pentalastrum asteracanthion, n. sp.

All five arms equal, club-shaped, at their thickened obtuse end three times as broad as at their base, twice as long as broad. Angles between the arms equal.

Dimensions.—Radius of each arm 0.2, basal breadth 0.03, distal breadth 0.08.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

2. Pentalastrum astropecten, n. sp.

All five arms equal, with five to six distinct, simple joints, the basal joint two-thirds as broad as the terminal joint, which bears a strong conical spine. Angles between the arms equal. (Resembles Pentinastrum asteriscus, Pl. , fig. 2, but has no patagium.)

Dimensions.—Radius of each arm 0.14, basal breadth 0.024, distal breadth 0.036.

Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.

Subgenus 2. Pentalastromma, Haeckel.

Definition.—Arms of different sizes, one odd arm larger than the two others; the opposite odd angle generally different from the four other angles.

3. Pentalastrum ophidiaster, n. sp. (Pl. , fig. 3).

Arms nearly triangular, at their obtuse truncated distal end twice as broad as at their base. Four arms equal, with five joints each; the fifth arm twice as long, with seven joints. Angles between the arms nearly equal; the odd angle a little larger.

Dimensions.—Radius of the larger odd arm 0.25, of the four smaller arms 0.15; basal breadth 0.035, distal breadth 0.07.

Habitat.—Pacific, central area, Station 274, surface.

4. Pentalastrum cometa, n. sp.

Arms nearly cylindrical, at their obtuse truncated distal end one and a half times as broad as at their base. Posterior odd arm very large, with eleven joints, about three times as long as the two lateral arms (with five joints each) and four times as long as the two anterior arms (with three joints each). Angles between the paired arms different; the two lateral angles smaller than the two posterior, and these smaller than the odd anterior angle.

Dimensions.—Radius of the odd posterior arm 0.5, of the lateral arms 0.25, of the anterior arms 0.18; basal breadth 0.05, distal breadth 0.08.

Habitat.—South Pacific, Station 288, surface.

Genus 241. Pentinastrum, Haeckel, 1881, Prodromus, p. 461.

Definition.—Porodiscida with five simple, undivided, chambered arms, connected by a patagium.

The genus Pentinastrum differs from the foregoing Pentalastrum only in the development of a patagium or connecticulum between the arms, and bears therefore the same relation to it that Histiastrum does to Stauralastrum, or Hymeniastrum to Dictyastrum.

1. Pentinastrum asteriscus , n. sp. (Pl. , fig. 2).

All arms equal, twice as long as broad, at their base two-thirds as broad as at their truncated distal end, which bears a strong, pyramidal, terminal spine. Each arm is divided by five transverse septa into six joints or chambers, and each of these by a radial beam into a pair of chambers. The five radial beams arise from the innermost chamber of the central disk, and end in the five terminal spines. The diameter of the central disk is larger than the length of the arms. The angles between the arms are equal and filled up by an incomplete patagium, so that the whole disk forms a regular pentagon with five concave sides.

Dimensions.—Radius of each arm (without terminal spine) 0.14; breadth at their base 0.02, at their terminal joint 0.03; radius of the central disk 0.06.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

2. Pentinastrum goniaster, n. sp.

? Stephanastrum sp., Bury, 1862, Polycystins of Barbados, pl. xx. fig. 1.

All five arms equal, four times as long as broad, club-shaped, at their globose distal end twice as broad as at their base, and armed with a strong conical terminal spine. Diameter of the central disk equals only one-third of the length of the arms. The articulation of the spongy arms is somewhat obscure. Patagium complete, totally fills up the interbrachial spaces, so that the whole disk forms a regular pentagon with five rectilinear sides, except that the terminal spines project at the corners.

Dimensions.—Radius of each arm 0.18, basal breadth 0.02, distal breadth 0.04; radius of the central disk 0.05.

Habitat.—South Pacific, Station 295, depth 1500 fathoms; also fossil in the rocks of Barbados.

Genus 242. Pentophiastrum, n. gen.

Definition.—Porodiscida with five forked chambered arms, without a patagium.

The genus Pentophiastrum differs from the two preceding genera by the bifurcation of the five arms, and can be derived either from Pentalastrum by the ramification of the distal ends of the arms, or from the similar Myelastrum by the increase in the number of arms.

1. Pentophiastrum dicranastrum, n. sp.

All five arms equal, with equal angles between them. Each arm in the basal half simple, in the distal half forked; both branches of it equal, with obtuse ends. (This regular species resembles Dicranastrum furcatum, Pl. , fig. 2, but with five rays instead of four; also the form of the arms is more slender and the edges smooth.)

Dimensions.—Radius of each arm 0.25, breadth 0.05.

Habitat.—Equatorial Atlantic, Station 347, depth 2250 fathoms.

Subgenus Pentophiastromma, Haeckel.

Definition.—Arms of different size, one odd arm opposite to the angle between both arm-pairs.

2. Pentophiastrum caudatum, n. sp. (Pl. , fig. 5).

Arms in pairs different; four arms in the basal half simple, in the distal half forked; the fifth (posterior) odd arm simple, undivided, cylindrical; the anterior pair a little smaller than the posterior; the neighboring branches of the two pairs on each side larger than the two others. Axes of the arms and their branches straight.

Dimensions.—Radius of the arms about 0.5, breadth 0.12.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

3. Pentophiastrum forcipatum, n. sp. (Pl. , fig. 4).

Arms in pairs different, all in the basal two thirds simple, in the distal third forked. Only in the posterior (odd) arm both branches are equal, in the four others unequal. The common axis of the posterior lateral pair is horizontal, perpendicular to the median line; the axes of the anterior pair are pincer-like, concavely curved towards the median line or principal axis.

Dimensions.—Radius of the arms about 0.5, breadth 0.14.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Genus 243. Hexalastrum, Haeckel, 1881, Prodromus, p. 461.

Definition.—Porodiscida with six simple chambered arms, without a patagium.

The genus Hexalastrum, together with the following Hexinastrum, encloses those Euchitonida in which the number of the chambered arms surrounding the central disk amounts to six. This is the highest number of these articulated marginal appendages which is reached in any Discoidea. Formerly (1881) in my Prodromus, p. 459, I supposed that the same number was reached also by one Coccodiscid, and called this genus Hexactura. Afterwards I was convinced that this form was also a Hexalastrum.

1. Hexalastrum palmanthum, n. sp.

All six arms equal, with equal angles between them. Each arm club-shaped, three times as long as broad, twice as broad at the thickened distal end as at the base, without a terminal spine.

Dimensions.—Radius of each arm 0.2, basal breadth 0.02, distal breadth 0.06.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

2. Hexalastrum crinanthum, n. sp.

All six arms equal, with equal angles between them. Each arm club-shaped, four times as long as broad, at the egg-shaped distal end three times as broad as in the linear basal part, provided with numerous short conical spines and one longer terminal spine. (Resembles Stauralastrum rhopalophorum, Pl. , fig. 1, but with six rays instead of four.)

Dimensions.—Radius of each arm 0.3, basal breadth 0.03, distal breadth 0.08.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

Subgenus Hexalastromma, Haeckel.

Definition.—Arms more or less different in size or form; shell bilateral.

3. Hexalastrum orchidaceum, n. sp. (Pl. , fig. 5).

Hexactura orchidacea, Haeckel, 1881, Prodromus, p. 459.

Arms different in length, so that two unequal opposite odd arms determine the main axis, and the four other arms lie on both sides of this as two different pairs. The proportion of their relative length is the following:—anterior lateral arms five, anterior odd arm six; posterior lateral arms seven, posterior odd arm eight. Each arm is club-shaped, two to three times as long as broad, and divided into six to eight joints by five to seven transverse septa; its distal end is armed with a terminal spine and twice as broad as its base.

Dimensions.—Radius of the posterior odd arm 0.4, of the anterior odd arm 0.3; of the posterior lateral pair 0.35, of the anterior lateral pair 0.25; basal breadth 0.08, distal breadth 0.16.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

Genus 244. Hexinastrum, Haeckel, 1881, Prodromus, p. 461.

Definition.—Porodiscida with six simple, undivided, chambered arms, connected by a patagium.

The genus Hexinastrum differs from its ancestral form Hexalastrum by the development of a patagium between the arms. The only observed species is regular.

1. Hexinastrum geryonidum, n. sp. (Pl. , fig. 4).

Hexalastrum geryonidum, Haeckel, 1879, Atlas (pl. xliv. fig. 4).

Disk quite regular with six radii; all six arms of the same size and form, at their broad, convexly rounded, smooth end five times as broad as at their narrow base, and little longer than broad. Each arm is divided by eight transverse septa into nine simple joints or chambers of the same height; the breadth of the distal chambers increases rapidly. The regular, hexagonal, central disk exhibits four concentric rings around the central chamber. Patagium between the arms incomplete, with concavely fluted edge.

Dimensions.—Radius of each arm 0.15, basal breadth 0.016, distal breadth 0.08; radius of the central disk 0.04.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.