Dimensions.—Diameter of the outer shell 0.12, middle 0.04, inner 0.016.
Habitat.—Central Pacific, Station 272, surface.
Genus 81. Hexacontarium,[[112]] n. gen.
Definition.—Cubosphærida with three concentric lattice-spheres and six simple spines of different size; one opposite pair larger than the two others.
The genus Hexacontarium exhibits to its ancestral form Hexacontium the same relation that Hexaloncharium bears to Hexalonche; the former is developed from the latter by duplication of the medullary shell. As two opposite spines of one pair are larger than the four others, they correspond to the three axes of a quadratic crystal.
1. Hexacontarium dentatum, n. sp.
Cortical shell with regular circular, hexagonally framed pores, twice as broad as the bars, with smooth surface. Radial proportion of the three spheres = 1 : 2 : 5. Six radial spines three-sided prismatic, half as broad as the inner medullary shell, with three dentated edges. Two opposite major spines longer than the shell diameter; four other minor spines only half as long as the radius. (Similar to Hexacontium clavigerum, Pl. [23], fig. 5, but distinct by the prolongation of the spines of one axis.)
Dimensions.—Diameter of the outer shell 0.15, middle 0.06, inner 0.03; length of the major spines 0.2, minor 0.04.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
2. Hexacontarium clavatum, n. sp.