Habitat.—South Pacific, Station 296, depth 1825 fathoms.
3. Hexancistra triserrata, n. sp. (Pl. [22], fig. 10).
Cortical shell thin walled, thorny, twice to three times as broad as the medullary shell; the two shells connected by six strong triangular beams. Inner shell spherical, with very small, regular, circular pores; ten to twelve on the half meridian. Bars as broad as the pores. Outer shell regularly octahedral, with eight triangular perfectly regular even faces, separated by eight prominent edges; the meshes circular, regular, about twelve to fourteen on the half meridian, two to three times as broad as the bars between them. Six strong radial spines, about as long as the diameter of the outer shell, three-sided prismatic, cuspidate; their three edges prominent, serrate, spirally twisted. Each spine bears about its middle three strong flattened lateral branches, nearly perpendicular to it, not serrated, and slightly curved.
Dimensions.—Diameter of the outer shell 0.13, inner 0.045; pores of the former 0.01, of the latter 0.004; length of the spine 0.12, breadth 0.014.
Habitat.—Central Pacific, Station 274, depth 2750 fathoms.
4. Hexancistra quadricuspis, n. sp. (Pl. [22], fig. 11).
Cortical shell thin walled, covered with short bristle-shaped by-spines, three and a half times as broad as the medullary shell. Pores of the latter regular circular, small; pores of the former three to six times as large, very irregular, roundish, double-edged. Six radial spines, three-sided prismatic, about as long as the shell diameter, with three wing-like, slightly twisted edges, which are prolonged towards the distal end into three curved horn-shaped branches.
Dimensions.—Diameter of the outer shell 0.17, inner 0.05; cortical pores 0.01 to 0.03, bars 0.005; medullary pores 0.003, bars 0.001; length of the spines 0.15, breadth 0.013.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.