Dimensions.—Diameter of the whole shell 0.22; distance between each two shells 0.02; length of the by-spines 0.05, of the main spines 0.2.
Habitat.—Indian Ocean, Cocos Islands, surface, Rabbe.
Definition.—Staurosphærida with spongy, spherical shell (with or without enclosed concentric lattice-shells).
Definition.—Staurosphærida with solid, spongy, spherical shell and four crossed simple spines.
The genus Staurodoras may be developed from Styptosphæra by the production of four crossed spines on the simple, spongy, spherical shell, which is composed of looser or denser irregular wicker-work, without enclosed medullary shell.
1. Staurodoras spongosphæra, n. sp.
Four crossed spines, two to three times as long as the diameter of the spongy sphere, three-sided prismatic, with three dentated and spirally contorted edges. (Form of Spongosphæra streptacantha, but without medullary shell and with four equal spines, crossed regularly at right angles.)
Dimensions.—Diameter of the sphere 0.25; length of the spines 0.4 to 0.7.
Habitat.—Central Pacific, Station 271, surface.
2. Staurodoras mojsisovicsi, Dunikowski.
Staurodoras mojsisovicsi, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. xlv. p. 28, Taf. v. fig. 56.
Four crossed spines, one and a half times as long as the diameter of the spongy sphere, three-sided pyramidal, with three smooth edges. (What Dunikowski describes as "inner canals" of the spines are their edges.)
Dimensions.—Diameter of the sphere 0.14; length of the spines 0.18 to 0.2. basal breadth 0.04.
Habitat.—Fossil in the Alpine Lias (Schafberg near Salzburg).
3. Staurodoras liassica, Dunikowski.
Staurodoras liassica, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. xlv. p. 28, Taf. v. fig. 57.
Four crossed spines, shorter than the diameter of the spongy sphere, conical or pyramidal (?).
Dimensions.—Diameter of the sphere 0.19; length of the spine 0.13, basal breadth 0.045.
Habitat.—Fossil in the Alpine Lias (Schafberg near Salzburg).
4. Staurodoras wandae, Dunikowski.
Staurodoras wandae, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss. Wien, Bd. xlv. p. 28, Taf. v. fig. 58.
Four crossed spines shorter than the radius of the spongy sphere, conical. (May be the young form of the preceding species.)
Dimensions.—Diameter of the sphere 0.14; length of the spines 0.06, basal breadth 0.05.
Habitat.—Fossil in the Alpine Lias (Schafberg near Salzburg).
Cubosphærida, Haeckel, 1881, Prodromus, p. 449.
Definition.—Sphæroidea with six radial spines on the surface of the spherical shell, opposite in pairs in the three dimensive axes, perpendicular one to another; living solitary (not associated in colonies).
The family Cubosphærida is distinguished from the other Sphæroidea by the possession of six radial spines, which are opposite in pairs in three different axes, one perpendicular to the other two. These three axes are the typical "dimensive axes," which are more or less differentiated in the Larcoidea. But in these latter the shell itself and the enclosed central capsule become affected by the unequal growth in the three axes, whilst in the former the capsule constantly, and commonly also the shell, remains spherical. Sometimes the shell assumes the form of a regular octahedron, from the six corners of which arise the six radial spines, indicating its three axes.
The most simple Cubosphærida are the Hexastylida, with one single, spherical lattice-shell. To this ancestral group all other subfamilies can be opposed as "Cubosphærida concentrica," as their carapace is composed of two or more concentric lattice-shells—two in the Hexalonchida, three in the Hexacontida, four in the Hexacromyida, five or more in the Hexacaryida. In all these four subfamilies the concentric shells are simple (not spongy), fenestrated spheres. In a sixth subfamily, in the Hexadorida, the shell is wholly or partially composed of irregular, spongy wicker-work or loose reticulations, with or without a medullary shell in the centre.
The Six Radial Spines of the Cubosphærida are normally opposite in pairs in the three dimensive axes, each of which is perpendicular to the other two. But in many species besides this normal form occur individual abnormalities, in which the six spines are not quite accurately opposed, but more or less divergent; and often also the three dimensive planes (determined each by two axes) are not quite regular, but more or less uneven. More rarely the six spines appear disposed in quite an irregular manner.
In the greater part of the Cubosphærida all six spines are quite equal, of the same size and form. But in some genera a more or less considerable differentiation takes place, so that two pairs or all three pairs of spines become different; very rarely, also both spines of one pair become unequal (probably only an individual abnormality). Those variations correspond to the differences between the crystalline systems. The common Cubosphærida, with three equal spine-pairs, correspond to the regular or cubic system, with three equal axes. The rarer forms (Hexastylarium, Hexaloncharium, Hexacontarium) exhibit two equal pairs and one different pair; they correspond to the quadratic system, with three perpendicular axes, two of which are equal, the third unequal. Still more rare are those forms (Hexastylidium, Hexalonchidium), in which all three pairs of spines are different, corresponding to the three unequal axes of the rhombic crystalline system.
|
I. Subfamily Hexastylida. (Shell one simple latticed sphere.) |
brace | All six radial spines simple, of equal size, | 72. Hexastylus. | ||
| Six spines of different sizes, all six simple. | brace | Two pairs equal, one pair different, | 73. Hexastylarium. | ||
| All three pairs different, | 74. Hexastylidium. | ||||
|
II. Subfamily Hexalonchida. (Shell composed of two concentric latticed spheres.) |
brace | All six radial spines of equal size. | brace | Spines simple, | 75. Hexalonche. |
| Spines branched, | 76. Hexancistra. | ||||
| Six spines simple, in pairs of different sizes. | brace | Two pairs equal, one pair different, | 77. Hexaloncharium. | ||
| All three pairs different, | 78. Hexalonchidium. | ||||
|
III. Subfamily Hexacontida. (Shell composed of three spheres.) |
brace | All six radial spines of equal size. | brace | Spines simple, | 79. Hexacontium. |
| Spines branched, | 80. Hexadendron. | ||||
| Six spines simple, of different sizes. | Two pairs equal, one pair different, | 81. Hexacontarium. | |||
|
IV. Subfamily Hexacromyida. (Four concentric spheres.) |
brace | All six radial spines of equal size. | Spines simple, no branched, | 82. Hexacromyum. | |
|
V. Subfamily Hexacaryida. (Five or more spheres.) |
brace | All six radial spines of equal size. | brace | Spines simple, | 83. Cubosphæra. |
| Spines branched, | 84. Hexacaryum. | ||||
|
VI. Subfamily Hexadorida. (Shell a spongy sphere, with or without an enclosed central medullary shell.) |
brace | All six radial spines of equal size, simple (not branched). | brace | Without latticed medullary shell, | 85. Cubaxonium. |
| With one single medullary shell, | 86. Hexadoras. | ||||
| With two medullary shells, | 87. Hexadoridium. | ||||
| I. Subfamily Hexastylida. (Shell one simple latticed sphere.) | ||||||
| All six radial spines simple, of equal size, | ||||||
| 72. Hexastylus. | ||||||
| Six spines of different sizes, all six simple. | ||||||
| Two pairs equal, one pair different, | ||||||
| 73. Hexastylarium. | ||||||
| All three pairs different, | ||||||
| 74. Hexastylidium. | ||||||
| II. Subfamily Hexalonchida. (Shell composed of two concentric latticed spheres.) | ||||||
| All six radial spines of equal size. | ||||||
| Spines simple, | ||||||
| 75. Hexalonche. | ||||||
| Spines branched, | ||||||
| 76. Hexancistra. | ||||||
| Six spines simple, in pairs of different sizes. | ||||||
| Two pairs equal, one pair different, | ||||||
| 77. Hexaloncharium. | ||||||
| All three pairs different, | ||||||
| 78. Hexalonchidium. | ||||||
| III. Subfamily Hexacontida. (Shell composed of three spheres.) | ||||||
| All six radial spines of equal size. | ||||||
| Spines simple, | ||||||
| 79. Hexacontium. | ||||||
| Spines branched, | ||||||
| 80. Hexadendron. | ||||||
| Six spines simple, of different sizes. | ||||||
| Two pairs equal, one pair different, | ||||||
| 81. Hexacontarium. | ||||||
| IV. Subfamily Hexacromyida. (Four concentric spheres.) | ||||||
| All six radial spines of equal size. | ||||||
| Spines simple, no branched, | ||||||
| 82. Hexacromyum. | ||||||
| V. Subfamily Hexacaryida. (Five or more spheres.) | ||||||
| All six radial spines of equal size. | ||||||
| Spines simple, | ||||||
| 83. Cubosphæra. | ||||||
| Spines branched, | ||||||
| 84. Hexacaryum. | ||||||
| VI. Subfamily Hexadorida. (Shell a spongy sphere, with or without an enclosed central medullary shell.) | ||||||
| All six radial spines of equal size, simple (not branched). | ||||||
| Without latticed medullary shell, | ||||||
| 85. Cubaxonium. | ||||||
| With one single medullary shell, | ||||||
| 86. Hexadoras. | ||||||
| With two medullary shells, | ||||||
| 87. Hexadoridium. | ||||||
Definition.—Cubosphærida with one single spherical lattice-shell.
Definition.—Cubosphærida with one simple lattice-sphere and six simple spines of equal size.
The genus Hexalonche is the most simple form of all Cubosphærida, and may be regarded as the common ancestral form of this family. It can be derived phylogenetically from Cenosphæra, by development of six radial spines on the surface of the simple spherical lattice-shell. These six simple spines are of equal size and opposite in pairs in the three dimensive axes, corresponding to the three equal axes of a cubic crystal.
Definition.—Pores regular or subregular, of nearly equal size and form; surface of the cortical shell smooth, without radial by-spines (other than the six main spines).
1. Hexastylus phænaxonius, n. sp. (Pl. 21, fig. 3).
Shell thin walled, with smooth surface. Pores subregular, hexagonal, five to six times as broad as the bars; nine to ten on the radius. Six spines triangular pyramidal, as long as the radius of the shell, as broad at the base as one pore.
Dimensions.—Diameter of the shell 0.13, pores 0.008 to 0.01, bars 0.0015; length of the spines 0.07, basal breadth 0.008 to 0.012.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
2. Hexastylus sapientum, n. sp.
Shell thin walled, with smooth surface. Pores regular, hexagonal, eight to ten times as broad as the bars; six to seven on the radius. Six spines bristle-shaped, longer than the diameter of the shell. (Lattice-work and spines similar to those of Heliosphæra actinota, Monogr. d. Radiol., Taf. ix. fig. 3.)
Dimensions.—Diameter of the shell 0.15, pores 0.016, bars 0.002; length of the spines 0.2, breadth 0.002.
Habitat.—North Atlantic, Station 354, surface.
3. Hexastylus thaletis, n. sp. (Pl. 21, fig. 4).
Shell thin walled, with smooth surface. Pores subregular, circular, hexagonally framed, somewhat funnel-shaped, of the same breadth as the bars; eight to nine on the radius. Six spines triangular pyramidal, with prominent edges, as long as the radius, three to four times as broad at the base as one pore.
Dimensions.—Diameter of the shell 0.1, pores and bars 0.005; length of the spines 0.05, basal breadth 0.02.
Habitat.—Tropical Pacific, Station 225, depth 4575 fathoms.
4. Hexastylus favosus, n. sp.
Shell thick walled, with smooth surface. Pores regular, circular, hexagonally framed, deep funnel-shaped, of the same breadth as the bars; six to seven on the radius. Six spines triangular pyramidal, as long as the diameter, twice as broad at the base as one pore.
Dimensions.—Diameter of the shell 0.12, pores and bars 0.01; length of the spines 0.12, basal breadth 0.02.
Habitat.—South Atlantic, Station 320, surface.
5. Hexastylus longissimus, n. sp.
Shell thick walled, with smooth surface. Pores regular, circular, hexagonally framed, of the same breadth as the bars; five to six on the radius. Six spines triangular prismatic, extremely elongated, ten to twenty times as long as the diameter of the shell, twice as broad as one pore.
Dimensions.—Diameter of the shell 0.08, pores and bars 0.008; length of the spines 1.0 to 1.5, breadth 0.015.
Habitat.—Tropical Atlantic, Station 347, surface.
6. Hexastylus minimus, n. sp. (Pl. 21, fig. 5).
Shell thin walled, with smooth surface. Pores subregular, circular, twice as broad as the bars; five to six on the radius. Six spines triangular pyramidal, scarcely as long as the radius, at the base half as broad as long.
Dimensions.—Diameter of the shell 0.05, pores 0.004, bars 0.002; length of the spines 0.02, basal breadth 0.01.
Habitat.—Tropical Pacific, Station 225, depth 4575 fathoms.
7. Hexastylus biantis, n. sp.
? Haliphormis hexacantha, Ehrenberg, 1872, L. N. 24, Taf. x. fig. 6.
Shell thin walled, smooth. Pores regular, circular, four times as broad as the bars; eight to nine on the radius. Six spines conical, as long as the radius, at the base as broad as one pore.
Dimensions.—Diameter of the shell 0.12, pores 0.012, bars 0.003; length of the spines 0.06, basal breadth 0.012.
Habitat.—Indian Ocean, Madagascar, surface, Rabbe.
8. Hexastylus pittaci, n. sp.
Shell thin walled, smooth. Pores regular, circular, ten to twelve times as broad as the bars; six to seven on the radius. Six spines triangular pyramidal, as long as the radius, as broad as one pore.
Dimensions.—Diameter of the shell 0.12, pores 0.02, bars 0.002; length of the spines 0.06, basal breadth 0.02.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
9. Hexastylus maximus, n. sp.
Shell thick walled, smooth. Pores regular, circular, twice as broad as the bars; twelve to sixteen on the radius. Six spines six-sided pyramidal, half as long as the radius, three times as broad as one pore.
Dimensions.—Diameter of the shell 0.3, pores 0.01, bars 0.005; length of the spines 0.08, basal breadth 0.03.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
10. Hexastylus periandri, n. sp.
Shell thick walled, smooth. Pores regular, circular, double-edged, four times as broad as the bars; six to seven on the radius. Six spines conical, as long as the radius, twice as broad as one pore.
Dimensions.—Diameter of the shell 0.2, pores 0.012, bars 0.003; length of the spines 0.1, basal breadth 0.025.
Habitat.—Tropical Atlantic, Station 335, depth 1425 fathoms.
Definition.—Pores regular or subregular, of nearly equal size and form; surface of the spherical shell spiny, covered with numerous conical or bristle-shaped radial by-spines.
11. Hexastylus solonis, n. sp. (Pl. 21, fig. 11).
Shell thick walled, covered with numerous bristle-shaped radial spines (one-third to one-half as long as the six main spines, arising from the lattice-knots). Pores regular, circular, enclosed by prominent, hexagonal frames, four to six times as broad as the bars; seven to eight on the radius. Six main spines triangular pyramidal, with spirally contorted prominent edges, as long as the radius, as broad at the base as one pore.
Dimensions.—Diameter of the shell 0.13, pores 0.01, bars 0.002; length of the spines 0.06 to 0.8, basal breadth 0.01.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
12. Hexastylus cochleatus, n. sp. (Pl. 21, fig. 1).
Shell thick walled, covered with numerous short, conical spines (about as large as one pore). Pores regular, circular, three times as broad as the bars; eight to nine on the radius. Six main spines triangular pyramidal, with prominent, spirally-twisted edges, as long as the diameter of the shell, and twice as broad at the base as one pore.
Dimensions.—Diameter of the shell 0.17, pores 0.015, bars 0.005; length of the spines 0.16, breadth 0.03.
Habitat.—Mediterranean, Corfu, Haeckel, surface.
13. Hexastylus setosus, Haeckel.
Acanthosphæra setosa, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 285, Taf. ix. fig. 11.
Shell thin walled, covered with numerous short, bristle-shaped spines (not larger than one pore). Pores regular, circular, four times as broad as the bars; thirteen to sixteen on the radius. Six main spines three-sided pyramidal, scarcely one-third as long as the radius. (In the figure of Ehrenberg, loc. cit., only four spines are in regular, crossed disposition, two others opposite in oblique direction; this is either an individual abnormality, or an error of drawing; the same species occurs with six spines exactly regularly disposed in the three dimensive axes.)
Dimensions.—Diameter of the shell 0.15; pores 0.008, bars 0.002; length of the spines 0.02 to 0.03, basal breadth 0.005.
Habitat.—Indian Ocean, Zanzibar, Pullen; Madagascar, Rabbe.
14. Hexastylus chilonis, n. sp.
Shell thin walled, covered with numerous bristle-shaped spines (as long as the radius). Pores regular, circular, twice as broad as the bars; eight to nine on the radius. Six main spines triangular pyramidal, with straight edges, as long as the diameter of the shell, as broad as two pores.
Dimensions.—Diameter of the shell 0.2, pores 0.02, bars 0.01; length of the spines 0.2, basal breadth 0.05.
Habitat.—South Atlantic, Station 325, surface.
15. Hexastylus cleobuli, n. sp.
Shell thick walled, covered with numerous short, conical spines (twice as large as one pore). Pores regular, circular, of the same breadth as the bars; twelve to thirteen on the radius. Six main spines conical, as long as the radius, three times as broad as one pore.
Dimensions.—Diameter of the shell 0.24, pores and bars 0.005; length of the spines 0.12, basal breadth 0.016.
Habitat.—South Pacific, Station 300, depth 1375 fathoms.
Definition.—Pores irregular, of unequal size or form; surface of the spherical shell smooth, without radial by-spines (other than the six main spines).
16. Hexastylus triaxonius, n. sp. (Pl. 21, fig. 2).
Shell thin walled, with smooth surface. Pores irregular, polygonal, three to six times as broad as the bars; four to six on the radius. Six spines triangular pyramidal, as long as the diameter of the shell, as broad at the base as one pore.
Dimensions.—Diameter of the shell 0.05, pores 0.004 to 0.008, bars 0.0015; length of the spines 0.04, basal breadth 0.006.
Habitat.—North Pacific, Station 253, depth 3125 fathoms.
17. Hexastylus dimensivus, n. sp. (Pl. 21, fig. 6).
Shell thin walled, with smooth surface. Pores irregular, polygonal, four to eight times as broad as the bars; eleven to thirteen on the radius. Six spines hexagonal pyramidal, as long as the radius, about three times as broad at the base as one pore.
Dimensions.—Diameter of the shell 0.13, pores 0.006 to 0.009, bars 0.0012; length of the spines 0.06, basal breadth 0.025.
Habitat.—North Pacific, Station 256, depth 2950 fathoms.
18. Hexastylus brevispinus, n. sp.
Shell thin walled, with smooth surface. Pores irregular, roundish, two to four times as broad as the bars; six to eight on the radius. Six spines triangular pyramidal, half as long as the radius, twice as broad as one pore.
Dimensions.—Diameter of the shell 0.2, pores 0.008 to 0.016, bars 0.004; length of the spines 0.05, basal breadth 0.025.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
19. Hexastylus longispinus, n. sp.
Shell thick walled, smooth. Pores irregular, roundish, two to three times as broad as the bars; three to four on the radius. Six spines triangular prismatical, two to three times as long as the diameter of the shell.
Dimensions.—Diameter of the shell 0.08, pores 0.008 to 0.012, bars 0.004; length of the spines 0.2, breadth 0.01.
Habitat.—North Atlantic, Station 353, surface.
20. Hexastylus marginatus, n. sp. (Pl. 21, fig. 10).
Shell thick walled, rough. Pores irregular, roundish, somewhat funnel-shaped double-edged, two to three times as broad as the bars; twelve to fourteen on the radius. Six spines three-sided pyramidal, somewhat longer than the radius, three times as broad as one pore.
Dimensions.—Diameter of the shell 0.15, pores 0.007 to 0.01, bars 0.004; length of the spines 0.1, basal breadth 0.025.
Habitat.—South Pacific, Station 295, depth 1500 fathoms.
21. Hexastylus conifer, n. sp.
Shell thick walled, rough. Pores irregular, roundish, scarcely broader than the bars; fifteen to sixteen on the radius. Six spines conical, as long as the radius, five to seven times as broad as one pore.
Dimensions.—Diameter of the shell 0.18, pores and bars 0.004 to 0.006; length of the spines 0.1, basal breadth 0.03.
Habitat.—Indian Ocean, Sunda Strait, Rabbe, surface.
Definition.—Pores irregular, of unequal size or form; surface of the spherical shell spiny, covered with numerous conical or bristle-shaped by-spines.
22. Hexastylus dictyotus, n. sp. (Pl. 21, figs. 8, 9).
Shell thin walled, spiny; short spines conical, smaller than the pore-breadth. Pores irregular, polygonal, five to seven times as broad as the bars; four to six on the radius. Six spines triangular pyramidal, longer than the radius, about as broad as one smaller pore.
Dimensions.—Diameter of the shell 0.09, pores 0.01 to 0.015, bars 0.002; length of the spines 0.06, basal breadth 0.01.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
23. Hexastylus hirsutus, n. sp.
Shell thin walled, densely covered with bristle-shaped, radial spines, half as long as the six main spines. Pores irregular, polygonal, three to four times as broad as the bars; eight to ten on the radius. Six spines triangular pyramidal, as long as the radius, twice as broad as one pore.
Dimensions.—Diameter of the shell 0.14, pores 0.005 to 0.008, bars 0.002; length of the spines 0.06, basal breadth 0.01.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
24. Hexastylus contortus, n. sp. (Pl. 21, fig. 12).
Shell thick walled, covered with bristle-shaped, radial spines, half as long as the radius. Pores irregular, roundish, two to three times as broad as the bars; seven to eight on the radius. Six spines triangular prismatic, in the distal half spirally twisted like a cork-screw (fig. 12); longer than the diameter of the shell, about as broad as one pore.
Dimensions.—Diameter of the shell 0.12, pores 0.006 to 0.008, bars 0.003; length of the spines 0.15, breadth 0.015.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
25. Hexastylus spiralis, n. sp. (Pl. 21, fig. 7).
Shell thick walled, covered with short conical spines. Pores irregular, roundish, two to three times as broad as the bars; five to six on the radius. Six spines triangular prismatic, with three thin, spirally contorted edges, two to three times as long as the diameter of the shell, about as broad as one large pore.
Dimensions.—Diameter of the shell 0.16, pores 0.01 to 0.02, bars 0.006; length of the spines 0.3 to 0.5, basal breadth 0.02.
Habitat.—Tropical Western Pacific, Station 225, depth 4475 fathoms.
Definition.—Cubosphærida with one simple lattice-sphere and six simple spines of different sizes; one opposite pair larger than the other two.
The genus Hexastylarium differs from its probable ancestral form, Hexastylus, by the unequal growth of the six simple spines; two opposite spines of one pair being more strongly developed than the four others, which are equal. They correspond therefore to the three axes of a quadratic crystal.
1. Hexastylarium heteraxonium, n. sp.
Cortical shell thin walled, smooth, with regular, hexagonal pores, three times as broad as the bars; eight to ten on the radius. Six spines three-sided pyramidal, at the base as broad as one pore. Two opposite major spines longer than the shell diameter; four others scarcely as long as the radius. (Similar to Hexastylus phænaxonius, Pl. 21, fig. 3, but differing in the unequal length of the spines.)
Dimensions.—Diameter of the shell 0.15, pores 0.12, bars 0.004; length of the two major spines 0.2, of the four minor 0.07.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
2. Hexastylarium quadratum, n. sp.
Shell very delicate, with smooth surface, and irregular, polygonal pores, separated by very thin bars. The form of the shell is not, as commonly, a sphere, but a geometrical square octahedron, one axis (with two opposite major spines) being nearly twice as long as the other two dimensive axes; four spines, opposite by pairs in the latter, are only half as long. The eight sides of the octahedral shell are even, equilateral-triangular. Spines angular, thin.
Dimensions.—Diameter of the shell in the major axis 0.18, in the minor 0.1; length of the major spines 0.24, minor 0.12.
Habitat.—South Pacific, Station 295, depth 1500 fathoms.
3. Hexastylarium elongatum, n. sp.
Shell thick walled, with spiny surface, and with irregular, roundish pores, two to four times as broad as the bars; eight to ten on the radius. Two opposite major spines, three to four times as long as the shell diameter, whilst the four other spines are very short, scarcely as long as the radius. All six spines at the base three-sided pyramidal, the two longer being cylindrical.
Dimensions.—Diameter of the shell 0.1; length of the major spines 0.3 to 0.4, of the minor 0.04, basal breadth 0.02.
Habitat.—North Pacific, Station 244, surface.
Definition.—Cubosphærida with one simple lattice-sphere and six simple spines in pairs different; the two opposite spines of each pair equal, the three pairs unequal.
The genus Hexastylidium differs from its probable ancestral form, Hexastylus, by the unequal growth of the six simple spines; the two spines of each pair reaching the same dimensions, whilst the three pairs are different. They correspond therefore to the three axes of a rhombic crystal.
1. Hexastylidium rhomboides, n. sp.
Shell thin walled, smooth, with irregular, polygonal pores and very thin bars. Its form is not, as commonly, a sphere, but a rhombic octahedron. The radial proportion of the three unequal dimensive axes = 1 : 2 : 4. The radial proportion of the three pairs of spines = 1 : 3 : 8. Spines thin cylindrical, at the base angular.
Dimensions.—Diameter of the major shell axis 0.2, middle 0.1, minor 0.05; length of the major spines 0.3, middle 0.12, minor 0.04.
Habitat.—Indian Ocean, Madagascar, Rabbe, surface.
2. Hexastylidium spirale, n. sp.
Shell thick walled, spherical, thorny, with irregular, roundish pores, three to five times as broad as the bars; six spines very stout, prismatic (as broad as one large pore), with three ring-like, spirally convoluted edges. Two opposite major spines of extraordinary length, ten to twelve times as long as the shell diameter, the two middle opposite spines being about as long as the latter, the two minor scarcely one-third as long. (Similar to Hexastylus spiralis, Pl. 21, fig. 7, but distinguished by the very unequal length of the spines.)
Dimensions.—Diameter of the shell 0.12; length of the major spines 1 to 1.5 mm., middle 0.15, minor 0.04.
Habitat.—Central Pacific, Station 266, surface.
Definition.—Cubosphærida with two concentric spherical lattice-shells.
Definition.—Cubosphærida with two concentric lattice-spheres and six simple spines of equal size.
The genus Hexalonche is the most simple form, and probably the common ancestral form, of all Hexalonchida, or those Cubosphærida which possess two concentric latticed spheres, connected by six radial beams. Commonly one shell is intracapsular (medullary shell) and the other extracapsular (cortical shell); but sometimes also both shells are extracapsular, and these forms may perhaps be better separated as a peculiar genus Hexadilemma. In Hexalonche all six simple spines are of equal size, and opposite by pairs in three equal dimensive axes, corresponding to the three equal axes of a tesseral crystal. It can be derived from Hexastylus by duplication of the lattice-shell.
Definition.—Pores of the cortical shell regular or subregular, of nearly equal size and similar form; surface smooth, without radial by-spines (other than the six main spines).