Shell thick walled, smooth. Pores regular, circular, twice as broad as the bars; twelve to sixteen on the radius. Six spines six-sided pyramidal, half as long as the radius, three times as broad as one pore.
Dimensions.—Diameter of the shell 0.3, pores 0.01, bars 0.005; length of the spines 0.08, basal breadth 0.03.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
10. Hexastylus periandri, n. sp.
Shell thick walled, smooth. Pores regular, circular, double-edged, four times as broad as the bars; six to seven on the radius. Six spines conical, as long as the radius, twice as broad as one pore.
Dimensions.—Diameter of the shell 0.2, pores 0.012, bars 0.003; length of the spines 0.1, basal breadth 0.025.
Habitat.—Tropical Atlantic, Station 335, depth 1425 fathoms.
Subgenus 2. Hexastylettus, Haeckel.
Definition.—Pores regular or subregular, of nearly equal size and form; surface of the spherical shell spiny, covered with numerous conical or bristle-shaped radial by-spines.
11. Hexastylus solonis, n. sp. (Pl. [21], fig. 11).