25. Hexastylus spiralis, n. sp. (Pl. [21], fig. 7).
Shell thick walled, covered with short conical spines. Pores irregular, roundish, two to three times as broad as the bars; five to six on the radius. Six spines triangular prismatic, with three thin, spirally contorted edges, two to three times as long as the diameter of the shell, about as broad as one large pore.
Dimensions.—Diameter of the shell 0.16, pores 0.01 to 0.02, bars 0.006; length of the spines 0.3 to 0.5, basal breadth 0.02.
Habitat.—Tropical Western Pacific, Station 225, depth 4475 fathoms.
Genus 73. Hexastylarium,[[102]] n. gen.
Definition.—Cubosphærida with one simple lattice-sphere and six simple spines of different sizes; one opposite pair larger than the other two.
The genus Hexastylarium differs from its probable ancestral form, Hexastylus, by the unequal growth of the six simple spines; two opposite spines of one pair being more strongly developed than the four others, which are equal. They correspond therefore to the three axes of a quadratic crystal.
1. Hexastylarium heteraxonium, n. sp.
Cortical shell thin walled, smooth, with regular, hexagonal pores, three times as broad as the bars; eight to ten on the radius. Six spines three-sided pyramidal, at the base as broad as one pore. Two opposite major spines longer than the shell diameter; four others scarcely as long as the radius. (Similar to Hexastylus phænaxonius, Pl. [21], fig. 3, but differing in the unequal length of the spines.)
Dimensions.—Diameter of the shell 0.15, pores 0.12, bars 0.004; length of the two major spines 0.2, of the four minor 0.07.