Page:Scientific results HMS Challenger vol 18 part 1.djvu/411

Rh 1. Cubosphæra cubaxonia, n. sp. (Pl. 24, fig. 8).

Hexacromyon cubaxonium, Haeckel, 1881, Prodrom. et Atlas.

Shell composed of five concentric spheres, with the radial proportion = 1 : 3 : 8 : 10 : 13. The two medullary shells with small regular, circular pores of the same breadth as the bars. Inner cortical shell (third shell) with large regular, circular pores, four times as broad as the bars, hexagonally framed. From each hexagon-corner arises a thin bristle-shaped radial by-spine, which at a fixed distance from the centre is united with the middle cortical shell (fourth shell), which has very small circular pores. The beginning of the fifth shell (outermost) is indicated by six small reticula, produced by the six main spines at equal distances from the centre. All five shells are united by six prismatic radial beams, ending outside in pyramidal furrowed spines.

Dimensions.—Diameter of the five shells—(A) 0.2, (B) 0.15, (C) 0.12, (D) 0.045, (E) 0.015.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

2. Cubosphæra concentrica, n. sp.

Shell composed of six concentric spheres, with the radial proportion = 1 : 2 : 6 : 7.5 : 9 : 11. The two medullary shells with regular, circular pores, twice as broad as the bars. The four cortical shells of the same structure, with irregular, roundish pores, three to four times as broad as the bars. The size of these pores and the breadth of their bars gradually increase towards the smooth surface. All six shells are connected by six thin three-sided prismatic radial beams, which are prolonged outside in six stronger spines, angular pyramidal, with smooth edges, as long as the shell radius.

Dimensions.—Diameter of the six shells—(A) 0.02 (B) 0.04, (C) 0.12, (D) 0.15, (E) 0.18, (F) 0.22.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Definition.— with five to six or more concentric lattice-shells and six branched spines of equal size.

The genus Hexacaryum is distinguished from the foregoing Cubosphæra by ramification of the six radial spines, and therefore exhibits the same relation to it that Hexancistra bears to Hexastylus, &c.

1. Hexacaryum arborescens, n. sp. (Pl. 23, figs. 4, 4a).

Shell composed of five, six, or more concentric shells, which are united by six very large radial spines. The two medullary shells spherical, inner with regular, circular, outer with irregular polygonal pores. All cortical shells (third and following) not spherical, but regular octahedral, with irregular polygonal meshes and thin bars. Radial spines prismatic, with three wing-like, spirally twisted edges, which at equal distances send out thin forked lateral branches (six on each