Dimensions.—Diameter of the sphere 0.6, of the central cube 0.02; length of the spines 0.15, distal thickness 0.02.
Habitat.—Central Pacific, Station 271, surface.
2. Centrocubus cladostylus, n. sp. (Pl. [18], fig. 1).
Radial spines thirty-two, club-shaped, at the distal end eight to ten times as broad as at the basal end. Eight primary spines arise from the eight corners of the regular, cubiform medullary shell, and from these, in the form of lateral branches, twenty-four secondary spines arise with concavely curved bases (three from the three denticulate edges of each spine, at nearly equal distances from the centre). The free distal end of each of the thirty-two spines is of the same shape, about half as long as the radius of the spongy sphere; framework much looser in the outer than in the inner part.
Dimensions.—Diameter of the sphere 0.8, of the central cube 0.02; length of the spines 0.2, distal thickness 0.02.
Habitat.—North Pacific, Station 256, surface.
3. Centrocubus polystylus, n. sp.
Radial spines sixty to eighty, club-shaped, four to six times as broad at the distal as at the basal end. Eight primary spines arise from the eight corners of the regular, cubiform medullary shell, the remainder either springing as lateral branches from the three denticulate corners of the former, or arising within the spongy framework, which is much denser and darker in the central than in the peripheral part. The free distal end of each spine is one-third as long as the radius.
Dimensions.—Diameter of the sphere 0.9, of the central cube 0.02; length of the spines 0.15, distal thickness 0.02.
Habitat.—South Pacific, Station 295, surface.