Page:Scientific results HMS Challenger vol 18 part 1.djvu/399

Rh 3. Hexaloncharium hystricinum, n. sp.

Cortical shell spherical, three times as broad as the medullary shell, and densely covered with oblique bristle-shaped by-spines. Pores irregular roundish. Two opposite major spines three-sided prismatic, longer than the shell diameter; four minor spines pyramidal, scarcely half as long as the shell radius. (Somewhat similar to Hexalonche hystricina, but distinct in the prolongation of two major spines.)

Dimensions.—Diameter of the outer shell 0.15, inner 0.05; length of the two major spines 0.2, four minor 0.03, basal breadth 0.02.

Habitat.—South Pacific, Station 288, surface.

Definition.— with two concentric lattice-spheres and six simple spines of different sizes in pairs; the two opposite spines of each pair equal, the three pairs unequal.

The genus Hexalonchidium exhibits the same relation to Hexalonche that Hexastylidium bears to Hexastylus; the growth of the three spine-pairs is different, whilst both spines of each pair are equal; they correspond therefore to the three axes of a rhombic crystal.

1. Hexalonchidium axonometrum, n. sp.

Cortical shell thin walled, covered with short bristle-shaped by-spines, twice as broad as the medullary shell; both with regular hexagonal meshes, twice to three times as broad as the bars (inner meshes half as broad as the outer). All three spine-pairs three-sided prismatic, of very different length but of equal breadth (equal to three pores). Major spine-pair twice as long as the shell diameter; middle pair about equal to the latter, minor scarcely half as long. (Similar to Hexalonche anaximandri, Pl. 22, fig. 5, but distinct in the different length of the spines.)

Dimensions.—Diameter of the outer shell 0.12, inner 0.06; length of the major spines 0.25, middle 0.1, minor 0.04.

Habitat.—Indian Ocean, Madagascar, surface, Rabbe.

Definition.— with three concentric, spherical, or octahedral lattice-shells.