Subfamily 3. Astracturida, Haeckel, 1881, Prodromus, p. 458

Definition.—Coccodiscida with two or more (commonly three or four) chambered radial arms on the margin of the disk, situated in its equatorial plane (with or without a connecting patagium between the arms).

Genus 204. Diplactura, Haeckel, 1881, Prodromus, p. 458.

Definition.—Coccodiscida with two opposite chambered arms on the margin of the circular disk, without a connecting patagium.

The genus Diplactura is the simplest form of the Astracturida, or of those Coccodiscida in which the margin of the disk bears chambered arms, situated in its equatorial plane. This subfamily corresponds to the Euchitonida among the Porodiscida, to the Spongobrachida among the Spongodiscida. In Diplactura there are only two free arms, opposite in one equatorial diameter (corresponding to Amphibrachium among the former, to Spongolena among the latter).

Subgenus 1. Diplacturium, Haeckel.

Definition.—Arms blunt at the distal end, without radial spines.

1. Diplactura diplobrachia, n. sp.

Phacoid shell twice as broad as the medullary shell, with six pores on its radius, without a perfect chambered ring around it. Arms club-shaped, one and a half times as long as the diameter of the phacoid shell, at the distal end rounded, blunt, as broad as the latter, at the base only half as broad.

Dimensions.—Diameter of the phacoid shell 0.08, of the medullary shell 0.04; length of the arms 0.12, basal breadth 0.04, distal breadth 0.08.

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

Subgenus 2. Diplactinium, Haeckel.

Definition.—Arms on the distal end armed with a radial terminal spine.

2. Diplactura diploconus, n. sp. (Pl. , fig. 5).

Amphiactura diploconus, Haeckel, 1877, MS. et Atlas (pl. xxxviii. fig. 5).

Phacoid shell three times as broad as the medullary shell, with eight pores on its radius, surrounded by a single chambered ring. Arms club-shaped, twice as long as the diameter of the phacoid shell, at the distal end as broad as the latter, at the base only half as broad. Both poles of the common axis of the arms are armed with a strong spindle-shaped terminal spine.

Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.03; length of the arms (without terminal spines) 0.17, basal breadth 0.05, distal breadth 0.09.

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

Genus 205. Amphiactura, Haeckel, 1881, Prodromus, p. 458.

Definition.—Coccodiscida with two opposite chambered arms on the margin of the circular disk, connected by a spongy patagium.

The genus Amphiactura differs from the foregoing Diplactura in the development of a patagium between the arms, and therefore bears the same relation to it as Amphymenium in the Porodiscida does to Amphibrachium, or Spongobrachium in the Spongodiscida does to Spongolene. In this and in the following Discoidea provided with a patagium, this connecting web constantly exhibits a different texture of its framework, which is sometimes more regularly chambered, at other times more irregularly spongy.

1. Amphiactura amphibrachia, n. sp. (Pl. , figs. 3, 4).

Phacoid shell three times as broad as the medullary shell, with eight pores on its radius. Arms nearly equilateral triangular, twice as long as the diameter of the phacoid shell, at the truncated distal end as broad as the latter, at the base only one-third as broad. Patagium a circular lenticular disk, enveloping only the basal third of the arms, with three to four concentric circular rings, divided into chambers by about forty radial beams, which are prolonged beyond the margin of the patagium into radial spines. The vertical section (fig. 4) shows that the chambers of each arm (eleven to twelve transverse rows in the radius) are disposed in two layers.

Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.03; length of the arms 0.18, basal breadth 0.03, distal breadth 0.09.

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

Genus 206. Trigonactura, Haeckel, 1881, Prodromus, p. 459.

Definition.—Coccodiscida with three chambered arms on the margin of the circular or triangular disk, without a connecting patagium.

The genus Trigonactura exhibits three radial arms, which in all known species are separated by three equal angles. The terminal points of the arm-axes are the corners of an equilateral triangle. It corresponds therefore to Dictyastrum among the Porodiscida.

Subgenus 1. Trigonacturium, Haeckel.

Definition.—Distal end of the arms blunt or truncated, without a terminal spine.

1. Trigonactura pythagoræ, Haeckel.

Astromma pythagoræ, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xxx. fig. 2.

Phacoid shell circular, twice as broad as the medullary shell, with five pores on its radius, without a completely surrounding chambered girdle. Arms nearly square, at the truncated distal end as broad as long, and scarcely broader than at the base, two-thirds as long as the diameter of the central disk.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.05; length of the arms 0.07, distal breadth 0.07.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, in various depths; also fossil in Tertiary rocks of Barbados and Nicobar.

2. Trigonactura rhopalastrella, n. sp.

Stephanastrum sp., Bury, 1862, Polycystins of Barbados, pl. xv. fig. 7.

Phacoid shell twice as broad as the medullary shell, with five pores on its radius, without a perfect chambered ring around it. Arms club-shaped, at the blunt distal end rounded, as long as the diameter of the phacoid shell; their basal breadth is one-fourth, their distal breadth one-half of its length.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.05; length of the arms 0.1, basal breadth 0.025, distal breadth 0.05.

Habitat.—Pacific, central area, Stations 270 to 274, depths 2400 to 2800 fathoms; also fossil in Tertiary rocks of Barbados.

3. Trigonactura trigonobrachia, n. sp.

Phacoid shell two and a half times as broad as the medullary shell, with six pores on its radius, without a perfect chambered girdle. Arms nearly equilateral triangular, twice as long as the diameter of the phacoid shell, at the truncated distal end as broad as its diameter and three times as broad as at the narrow base. (Resembles Hymenactura hexagona, but without a patagium.)

Dimensions.—Diameter of the phacoid shell 0.11, of the medullary shell 0.045; length of the arms 0.2, basal breadth 0.035, distal breadth 0.1.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

4. Trigonactura lanceolata, n. sp.

Phacoid shell three times as broad as the medullary shell, with eight pores on its radius, surrounded by one perfect chambered ring. Arms lanceolate, three times as long as the diameter of the phacoid shell, and four times as long as broad in the middle part, at both ends very narrow, blunt.

Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.03; length of the arms 0.25, breadth in the midst 0.06.

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

Subgenus 2. Trigonactinium, Haeckel.

Definition.—Distal end of the arms armed with a radial spine.

5. Trigonactura triacantha, n. sp. (Pl. , figs. 6, 7).

Phacoid shell two and a half times as broad as the medullary shell, with eight pores on its radius, surrounded by one perfect chambered ring. Arms nearly lanceolate, in the middle part one and a half times as broad as at both ends, twice as long as the phacoid shell, at the distal end with a strong pyramidal terminal spine. Through the spongy framework of each arm shine sixteen to eighteen transverse bars (as septa of the joints) and six to eight longitudinal piercing beams.

Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.038; length of the arms 0.2, greatest breadth 0.08.

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

6. Trigonactura trigonodiscus, n. sp.

? Astromma sp., Bury, 1862, Polycystins of Barbados, Taf. xv. fig. 2.

Phacoid shell triangular, twice as broad as the spherical medullary shell, with six to seven pores on its radius, surrounded by one chambered ring. Arms equilateral triangular, as long as the diameter of the central disk and at the base half as broad, slowly decreasing in breadth towards the distal end, which is armed with a strong pyramidal spine.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.05; length of the arms 0.12, basal breadth 0.07.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms; also fossil in Barbados.

7. Trigonactura trixiphos, n. sp.

Phacoid shell circular, twice as broad as the medullary shell, without a completely surrounding chambered ring, with four pores on its radius. Arms club-shaped, about as long as the diameter of the central disk, at the base half as broad as long, at the rounded distal end broader, and armed with a strong pyramidal terminal spine, nearly as long as the arm itself.

Dimensions.—Diameter of the phacoid shell 0.08, of the medullary shell 0.04; length of the arms (without terminal spine) 0.08, basal breadth 0.04, distal breadth 0.06.

Habitat.—Fossil in the rocks of Barbados.

Genus 207. Hymenactura, Haeckel, 1881, Prodromus, p. 459.

Definition.—Coccodiscida with three chambered arms on the margin of the circular or triangular disk, connected by a spongy patagium.

The genus Hymenactura differs from the foregoing Trigonactura in the spongy patagium between the arms, and bears therefore to it the same relation that among the Porodiscida Hymeniastrum does to the simpler Dictyastrum. The oldest known species of this genus is Hymenactura pythagoræ, described by Ehrenberg as Hymeniastrum pythagoræ, but differing from this in the structure of the central disk.

Subgenus 1. Hymenacturium, Haeckel.

Definition.—Distal end of the arms blunt or truncated, without terminal spines.

1. Hymenactura archimedis, n. sp. (Pl. , fig. 8).

Phacoid shell three times as broad as the medullary shell, with eight pores on its radius. Arms nearly trapezoidal, somewhat longer than the diameter of the central disk, at the truncated distal end nearly as broad, at the base only half as broad. In each arm eleven to twelve transverse rows of square chambers, each of which exhibits on the surface one large pore. Patagium enveloping the basal half of the arms, with four to five convex rows of chambers, forming together a circular concentric disk.

Dimensions.—Diameter of the phacoid shell 0.11, of the medullary shell 0.035; length of the arms 0.12, basal breadth 0.05, distal breadth 0.1.

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

2. Hymenactura pythagoræ, Haeckel.

Hymeniastrum pythagoræ, Ehrenberg, 1854, Mikrogeol., Taf. xxxvi. fig. 31; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 76, Taf. xxx. fig. 5.

Phacoid shell three times as broad as the medullary shell, with six pores on its radius. Arms nearly trapezoidal, somewhat longer than the diameter of the central disk, at the truncated distal end nearly as broad, at the base two-thirds as broad. In each arm eight to nine transverse rows of square chambers, each chamber with one pore on the surface. Patagium enveloping the basal half of the arms, with four to five rectilinear parallel rows of chambers, forming together a regular triangle. Differs from the preceding species mainly in the quite different structure of the patagium, from the true Hymeniastrum pythagoræ in the phacoid shell of the central disk, which encloses only one simple medullary shell.

Dimensions.—Diameter of the phacoid shell 0.11, of the medullary shell 0.04; length of the arms 0.13, basal breadth 0.07, distal breadth 0.12.

Habitat.—Fossil in the rocks of Barbados.

3. Hymenactura trigona, n. sp.

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

Phacoid shell twice as broad as the medullary shell, with four to five pores on its radius. Arms slender, lanceolate, three times as long as the diameter of the phacoid shell and five times as long as broad in the middle part; distal ends blunt. Patagium enveloping only the basal half of the arms, forming a regular triangle with concave sides.

Dimensions.—Diameter of the phacoid shell 0.08, of the medullary shell 0.035; length of the arms 0.2, greatest breadth 0.04.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms; fossil in the rocks of Barbados.

4. Hymenactura hexagona.

Hymeniastrum sp., Bury, 1862, Polycystins of Barbados, pl. xv. fig. 3.

Phacoid shell twice as broad as the medullary shell, with four to five pores on its radius. Arms nearly equilateral triangular, three times as long as the diameter of the phacoid shell, at the truncated distal end nearly three-fourths as broad as long, at the narrow base only one-fourth as broad. Patagium complete, enveloping the arms completely, so that the whole body represents a regular hexagonal disk.

Dimensions.—Diameter of the phacoid shell 0.08, of the medullary shell 0.04; length of the arms 0.18, basal breadth 0.04, distal breadth 0.16.

Habitat.—Fossil in the rocks of Barbados and Nicobar.

Subgenus 2. Hymenactinium, Haeckel.

Definition.—Distal ends of the arms armed with terminal spines.

5. Hymenactura ptolemæi, n. sp.

Astromma sp., Bury, 1862, Polycystins of Barbados, pl. xv. figs. 5, 6.

Phacoid shell twice as broad as the medullary shell, with six to seven pores on its radius. Arms nearly square, about as large as the phacoid shell, at the truncated distal end little broader than at the base, and armed with a strong pyramidal terminal spine. Patagium incomplete, enveloping the basal half of the arms.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.05; length and greatest breadth of the arms 0.08.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms; fossil in the rocks of Barbados.

6. Hymenactura copernici, n. sp. (Pl. , fig. 9).

Phacoid shell three times as broad as the medullary shell, with six pores on its radius. Arms lanceolate, nearly twice as long as the phacoid shell, in the middle part twice as broad as the medullary shell, with a strong conical terminal spine at the distal end. In each arm about ten transverse rows of chambers. Patagium enveloping the basal half of the arms, with four convex parallel rows of chambers.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.035; length of the arms 0.17, greatest breadth 0.07.

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

Genus 208. Astractura, Haeckel, 1881, Prodromus, p. 459.

Definition.—Coccodiscida with four chambered arms on the margin of the circular or quadrangular disk, crossed in two equatorial diameters, without a connecting patagium.

The genus Astractura has the form of a regular cross, four radial arms being opposite in two equatorial diameters perpendicular one to another. In the Porodiscida the same form is repeated by Stauralastrum, in the Spongodiscida by Spongasteriscus. The oldest known species of the genus is Astromma aristotelis of Ehrenberg, in which genus this author confounded triradial and four-radial forms.

Subgenus 1. Astracturium, Haeckel.

Definition.—Distal end of the arms blunt or truncated, without terminal spines.

1. Astractura ordinata, n. sp.

? Astromma sp., Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 3.

Phacoid shell three times as broad as the medullary shell, with six pores on its radius, without a completely developed chambered ring. Arms trapezoidal, somewhat longer than the radius of the disk, at the truncated distal end as broad as long, at the base one-third smaller.

Dimensions.—Diameter of the phacoid shell 0.08, of the medullary shell 0.03; length of the arms 0.05, distal breadth 0.05, basal breadth 0.035.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms; also fossil in Barbados.

2. Astractura clavigera, n. sp.

Astromma aristotelis, Bury, 1862, Polycystins of Barbados, pl. iv. fig. 2.

Phacoid shell twice as broad as the medullary shell, with ten pores on its radius, surrounded by one perfect chambered ring. Arms club-shaped, about as long as the radius of the central disk, at the rounded distal end two-thirds, at the base one-third as broad as long.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.05; length of the arms 0.06, basal breadth 0.02, distal breadth 0.04.

Habitat.—Pacific, central area, Stations 270 to 274, depths 2350 to 2925 fathoms; fossil in the rocks of Barbados.

Subgenus 2. Astractinium, Haeckel.

Definition.—Distal end of the arms furnished with a radial spine.

3. Astractura aristotelis, Haeckel.

Astromma aristotelis, Ehrenberg, 1856, Microgeol., Taf. xxxvi. fig. 32; Abhandl. d. k. Akad. d. Wiss. Berlin, 1875, p. 66, Taf. xxx. fig. 4.

Astromma aristotelis, Haeckel, 1862, Monogr. d. Radiol., p. 489.

? Astromma aristotelis, Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 4.

Phacoid shell three times as broad as the medullary shell, with six to eight pores on its radius, surrounded by one perfect chambered ring. Arms nearly trapezoidal, about as long as the diameter of the central disk, at the base half as broad, at the truncated distal end nearly as broad as long, and armed with a large pyramidal terminal spine. Each arm with about eight transverse and longitudinal rows of chambers.

Dimensions.—Diameter of the phacoid shell 0.11, of the medullary shell 0.04; length of the arms 0.1, basal breadth 0.05, distal breadth 0.09.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, at various depths; fossil in the Tertiary rocks of Barbados and Nicobar.

4. Astractura democriti, n. sp.

Astromma aristotelis, var., Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf, xxx. fig. 3.

? Astromma aristotelis, var., Bury, 1862, Polycystins of Barbados, pl. xiv. fig. 4.

Phacoid shell twice as broad as the medullary shell, with five to seven pores on its radius, without perfect chambered ring. Arms about twice as long as broad, longer than the diameter of the central disk, at the truncated distal end a little broader than at the base, and armed with a strong, pyramidal, terminal spine.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.05; length of the arms 0.15, basal breadth 0.04, distal breadth 0.08.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms; fossil in Barbados.

5. Astractura hippocratis, n. sp.

Phacoid shell three times as broad as the medullary shell, with seven pores on its radius, surrounded by two to three perfect chambered rings. Arms nearly square, scarcely as long and nearly as broad as the diameter of the central disk, at the rounded distal end armed with a very strong, pyramidal, terminal spine, longer than the arm itself, and at the base as broad as the medullary shell.

Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.03; length of the arms 0.08, breadth 0.1.

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

Genus 209. Stauractura, Haeckel, 1881, Prodromus, p. 459.

Definition.—Coccodiscida with four chambered arms on the margin of the circular or quadrangular disk, crossed in two equatorial diameters, connected by a spongy patagium.

The genus Stauractura differs from the foregoing in the patagium between the arms, and bears therefore the same relation to it as Histiastrum in the Porodiscida does to Stauralastrum. All known species of this genus form a regular square, if we connect the end points of the arm axes by lines.

Subgenus 1. Stauracturium, Haeckel.

Definition.—Distal end of the arms blunt or truncated, without terminal spines.

1. Stauractura octogona, n. sp.

Phacoid shell twice as broad as the medullary shell, with eight pores in its radius. Arms nearly square, little larger than the phacoid shell, with broad truncated distal ends. The corners of the latter are so connected by the complete patagium, that the whole shell forms a regular octagon.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.05; length of the arms 0.12, distal breadth 0.11.

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

2. Stauractura tetragona, n. sp.

Phacoid shell three times as broad as the medullary shell, with eleven pores on its radius. Arms club-shaped, nearly as long as the diameter of the phacoid shell, and one and a half times as long as broad at the distal part; at the distal end rounded, blunt, without terminal spine. The terminal points of the arms are so connected by a thin, complete patagium, that the whole shell becomes a regular square.

Dimensions.—Diameter of the phacoid shell 0.13, of the medullary shell 0.045; length of the arms 0.12, greatest breadth 0.08.

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

Subgenus 2. Stauractinium, Haeckel.

Definition.—Distal end of the arms furnished with a radial spine.

3. Stauractura medusina, n. sp.

Phacoid shell two and a half times as broad as the medullary shell, with nine pores on its radius. Arms club-shaped, one and a half times as long as the diameter of the phacoid shell, and in the outer third nearly as broad as the latter, at the base scarcely one-third as broad; their truncated distal end armed with a strong pyramidal terminal spine. Patagium incomplete, enveloping only the basal half of the arms, with three rectilinear parallel rows of chambers, forming a square.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.04; length of the arms 0.14, greatest breadth 0.08.

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

4. Stauractura quadrata, n. sp.

Phacoid shell twice as broad as the medullary shell, with seven pores on the radius. Arms nearly square, about as large as the phacoid shell, with a strong pyramidal terminal spine at the distal end. Patagium complete, between every two arms triangular, with rectilinear parallel rows of chambers; it connects the end points of the arm radius in such a manner that the whole shell becomes a regular square.

Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.045; length of the arms 0.1, greatest breadth 0.08.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

Genus 210. Pentactura, Haeckel, 1881, Prodromus, p. 459.

Definition.—Coccodiscida with five chambered arms on the margin of the circular or pentagonal disk, without a connecting patagium.

The genus Pentactura possesses five free radial arms, and resembles Pentalastrum among the Porodiscida. The distance of the five arms seems to be sometimes equal, at other times different in one and the same species.

1. Pentactura pentactis, Haeckel.

Astromma pentactis, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 66, Taf. xxx. fig. 1.

Phacoid shell two and a half times as broad as the medullary shell, with eight pores on its radius. Arms regularly or irregularly disposed, nearly square, about half as large as the phacoid shell, at the truncated distal end little broader than at the base. In the specimen figured, and very imperfectly described by Ehrenberg, (loc. cit.), the arms were asymmetrically disposed, two opposite in one axis of the disk, two others on one side of this axis, the fifth opposite to these on the other side. Another specimen which I found in the Barbados rocks had five arms of equal size, regularly disposed, at equal intervals.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.04; length and breadth of the arms 0.05 to 0.06.

Habitat.—Fossil in the rocks of Barbados.

2. Pentactura astropecten, n. sp.

Phacoid shell three times as broad as the medullary shell, with ten pores on its radius. Arms regularly disposed, club-shaped, nearly twice as long as the diameter of the phacoid shell, and equal to it in breadth at the rounded distal end. The latter is armed with a short conical spine, and is twice as broad as the base.

Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.03; length of the arms 0.17, basal breadth 0.05, distal breadth 0.08.

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

Genus 211. Echinactura, n. gen.

Definition.—Coccodiscida with five chambered arms on the margin of the circular or pentagonal disk, connected by a spongy patagium.

The genus Echinactura differs from the foregoing Pentactura in the patagium between the arms, and bears therefore the same relation to it as Pentinastrum in the Porodiscida does to Pentalastrum.

1. Echinactura culcita, n. sp.

Phacoid shell pentagonal, three times as broad as the medullary shell, with nine pores on its radius. Arms egg-shaped, about as long as the diameter of the phacoid shell, and in the distal part half as broad. The blunt ends of the arms are so connected by the complete patagium that the whole shell becomes a regular pentagonal disk.

Dimensions.—Diameter of the phacoid shell 0.1, of the medullary shell 0.035; length of the arms 0.11, basal breadth 0.04, distal breadth 0.06.

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

2. Echinactura asteriscus, n. sp.

Phacoid shell twice as broad as the medullary shell, with seven pores on its radius. Arms lanceolate, twice as long as the diameter of the phacoid shell, in the middle part nearly as broad as the latter, at the distal end with a strong conical terminal spine. Patagium incomplete, enveloping only the basal half of the arms.

Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.045; length of the arms 0.2, greatest breadth 0.08.

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

3. Echinactura goniaster, n. sp.

Phacoid shell three times as broad as the medullary shell, with nine pores on its radius. Arms club-shaped, one and a half times as long as the diameter of the phacoid shell, in the distal part nearly as broad as the latter, in the basal part one-third as broad; at the end a strong pyramidal spine. Patagium nearly complete, with concave dentated margin between each pair of arms, therefore the pentagonal disk of the whole shell with concave sides.

Dimensions.—Diameter of the phacoid shell 0.12, of the medullary shell 0.04; length of the arms (without terminal spine) 0.18, basal breadth 0.04, distal breadth 0.1.

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