Cortical shell smooth, three to four times as broad as the spherical medullary shell, each having regular circular pores, twice to three times as broad as the bars. Form of the outer shell not a sphere, but a regular octahedron, with eight congruent, equilateral triangular even faces. Two opposite spines twice as long as the shell diameter, whilst the four others are scarcely equal to it. Basal breadth of all six the same (three times as large as one pore); form, three-sided prismatic, with cuspidate distal end. (Similar to Hexalonche octahedra, Pl. [22], fig. 8, but distinct in the unequal length of the spines.)
Dimensions.—Diameter of the outer shell 0.16, inner 0.045; length of the major spine 0.3, minor 0.12, basal breadth 0.03.
Habitat.—South Atlantic, Station 332, depth 2200 fathoms.
2. Hexaloncharium philosophicum, n. sp.
Cortical shell spherical, covered with short conical by-spines, twice as broad as the medullary shell; both with regular circular pores three to four times as broad as the bars. Two major spines cylindrical, with conical apex, three times as long as the four others, which are conical and about as long as the shell radius; basal breadth of all six the same (equal to one pore). Similar to Hexalonche anaximenis (Pl. [25], fig. 5), but distinct in the enormous prolongation of two opposite spines.
Dimensions.—Diameter of the outer shell 0.12, inner 0.06; length of the two major spines 0.2, of the four minor 0.06, basal breadth 0.02.
Habitat.—Central Pacific, Station 267, depth 2700 fathoms.
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.