Page:Scientific results HMS Challenger vol 18 part 1.djvu/398

190 Dimensions.—Diameter of the outer shell 0.13, of the inner 0.05; length of the spines 0.5 to 0.8 or more, breadth 0.02.

Habitat.—Central Pacific, Station 271, surface.

Definition.— with two concentric lattice-spheres and six simple spines of different sizes; one opposite pair larger than the two others.

The genus Hexaloncharium exhibits the same relation to its ancestral form, Hexalonche, that Hexastylarium bears to Hexastylus. Two opposite spines of one pair are larger than the four others, and correspond to the three axes of a quadratic crystal.

1. Hexaloncharium octahedrum, n. sp.

Cortical shell smooth, three to four times as broad as the spherical medullary shell, each having regular circular pores, twice to three times as broad as the bars. Form of the outer shell not a sphere, but a regular octahedron, with eight congruent, equilateral triangular even faces. Two opposite spines twice as long as the shell diameter, whilst the four others are scarcely equal to it. Basal breadth of all six the same (three times as large as one pore); form, three-sided prismatic, with cuspidate distal end. (Similar to Hexalonche octahedra, Pl. 22, fig. 8, but distinct in the unequal length of the spines.)

Dimensions.—Diameter of the outer shell 0.16, inner 0.045; length of the major spine 0.3, minor 0.12, basal breadth 0.03.

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

2. Hexaloncharium philosophicum, n. sp.

Cortical shell spherical, covered with short conical by-spines, twice as broad as the medullary shell; both with regular circular pores three to four times as broad as the bars. Two major spines cylindrical, with conical apex, three times as long as the four others, which are conical and about as long as the shell radius; basal breadth of all six the same (equal to one pore). Similar to Hexalonche anaximenis (Pl. 25, fig. 5), but distinct in the enormous prolongation of two opposite spines.

Dimensions.—Diameter of the outer shell 0.12, inner 0.06; length of the two major spines 0.2, of the four minor 0.06, basal breadth 0.02.

Habitat.—Central Pacific, Station 267, depth 2700 fathoms.