Subfamily Hexadorida, Haeckel, 1881, Prodromus, pp. 449, 455

Definition.—Cubosphærida with spongy spherical or octahedral shell (with or without enclosed concentrical lattice-shells).

Genus 85. Cubaxonium, n. gen.

Definition.—Cubosphærida with solid spongy spherical or octahedral shell, without latticed medullary shell in the centre, and with six simple radial spines of equal size.

The genus Cubosphæra may be regarded as a form of Styptosphæra, which develops six radial spines, opposite in pairs in the three dimensive axes. The solid spongy framework of the shell assumes the outer form either of a sphere, or of a regular octahedron.

1. Cubaxonium spongiosum, n. sp.

Spongy shell spherical, composed of a very dense spongy framework of nearly uniform structure; the meshes three to four times as broad as the bars; surface almost smooth. Six spines cylindrical, twice to three times as long as the diameter of the spongy sphere, about as broad as one half mesh.

Dimensions.—Diameter of the sphere 0.2, meshes 0.006 to 0.008, bars 0.002; length of the spines 0.4 to 0.5, breadth 0.004.

Habitat.—South Pacific, Station 288, surface.

2. Cubaxonium octahedrum, n. sp.

Spongy shell octahedral, composed of a loose spongy framework of nearly uniform structure; the meshes ten to twelve times as broad as the bars; surface thorny. Six spines three-sided pyramidal, longer than the diameter of the octahedron, arising from its six corners, as broad at the base as one mesh.

Dimensions.—Diameter of the shell 0.15, meshes 0.01 to 0.012, bars 0.001; length of the spines 0.2, basal breadth 0.01.

Habitat.—South Pacific, Station 300, surface.

Genus 86. Hexadoras, Haeckel, 1881, Prodromus, p. 455.

Definition.—Cubosphærida with spongy spherical shell and one simple latticed medullary shell in its centre, having six simple spines of equal size.

The genus Hexadoras exhibits the same structure of the spongy shell as Spongoplegma, but differs from it in the production of six dimensive spines. In the centre lies one simple, latticed, medullary shell, which is either spherical or octahedral. In the latter case the six spines arise from the six corners of the octahedron.

1. Hexadoras axophæna, n. sp.

Medullary shell spherical, with regular hexagonal meshes, twice as broad as the bars. Cortical shell entirely enclosing it, with loose irregular framework and thorny surface. Diameter of the outer shell three times as large as that of the inner. Six radial spines arising from the medullary shell, four to five times as long as the radius of the cortical shell, three-sided prismatic, with straight dentated edges.

Dimensions.—Diameter of the outer shell 0.15, inner 0.05; length of the spines 0.3 to 0.4.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Hexadoras lychnosphæra, n. sp.

Medullary shell spherical, with regular, circular, hexagonally framed pores, three times as broad as the bars. Cortical shell enveloping it, with loose irregular framework and spiny surface. Diameter of the outer shell eight times as large as that of the inner. Six radial spines arising from the inner shell, three-sided prismatic, with dentated, spirally contorted edges, seven times as long as the diameter of the medullary shell, with three lateral branches at the distal end (similar to Lychnosphæra, Pl. , fig. 1).

Dimensions.—Diameter of the outer shell 0.5, inner 0.06; total length of the spines 0.4, breadth 0.01.

Habitat.—Central Pacific, Station 270, depth 2925 fathoms.

3. Hexadoras octahedrum, n. sp.

Medullary shell regular octahedral, with irregular polygonal meshes, five times as broad as the bars. Cortical shell enveloping it, with dense spongy framework, also octahedral with rough surface. Diameter of the outer shell five times as large as that of the inner. Six radial spines very long, arising from the six corners of the inner and piercing the spongy mass of the outer shell, considerably exceeding it at the free distal end, three-sided prismatic, with elegantly denticulate edges.

Dimensions.—Diameter of the outer shell 0.2, inner 0.04; total length of the spines 0.3 or more, breadth 0.02.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

Genus 87. Hexadoridium, Haeckel, 1881, Prodromus, p. 455.

Definition.—Cubosphærida with spongy spherical shell and two concentric latticed medullary shells in its centre, having six simple spines of equal size.

The genus Hexadoridium differs from Hexadoras in the duplication of the medullary shell, and exhibits therefore the same relation to it that Spongodictyon bears to Spongoplegma. In the only known species the six spines are opposite, arranged quite regularly in pairs in the three dimensive axes, and consequently represent the three axes of a regular crystal or cube.

1. Hexadoridium streptacanthum, n. sp. (Pl. , figs. 1, 1a).

Both medullary shells spherical, with small regular, circular pores, twice as broad as the bars; outer twice as broad as the inner. Spongy cortical shell enclosing it with dense framework, five times as broad as the outer medullary shell, regular octahedral. Six radial spines, arising from the latter, are thinned at the inner end, three to five times as long as the diameter of the cortical shell, and nearly as broad as the inner medullary shell, with three dentated and spirally contorted edges. (Very similar to the common Spongosphæra streptacantha, with irregular and variable number and dispositions of spines; possibly its ancestral form?).

Dimensions.—Diameter of the cortical shell 0.2, of the outer medullary shell 0.04, inner 0.02; length of the spines 1 mm. and more, breadth 0.02.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.