Dimensions.—Longer axis of the cortical shell 0.16, shorter axis 0.12; pores 0.016, bars 0.006; diameter of the medullary shell 0.06; length of the polar spines 0.02 to 0.03, basal thickness the same.
Habitat.—Central area of the Pacific, Station 268, depth 2900 fathoms.
Subgenus 2. Lithatractylis, Haeckel.
Definition.—Network of the outer shell regular, with meshes of equal size and similar form; surface thorny or papillose, covered with small conical spines or tubercles.
6. Lithatractus echiniscus, n. sp.
Outer shell thorny, thin walled, with regular network; meshes circular, with hexagonal frame, four to five times as broad as the thin bars; eighteen to twenty on the half equator. From every corner between the three meshes, where three hexagons unite, starts one short, straight, triangular thorn (as in Ellipsoxiphus elegans, Pl. [14], fig. 7). Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Minor axis twice the diameter of the inner spherical shell, the pores of which are half as broad, circular. Polar spines three-sided pyramidal, about as long as the minor axis, as broad at the base as one hexagonal frame.
Dimensions.—Longer axis of the cortical shell 0.08, shorter axis = 0.06; pores 0.004, bars 0.001; length of the polar spines 0.05, basal thickness 0.005; diameter of the inner shell 0.03.
Habitat.—South Atlantic, off Tristan da Cunha, Station 334, surface.
7. Lithatractus carduelis, n. sp.
Outer shell thin walled, thorny, with regular network; meshes circular, simple, four to six times as broad as the thin bars; ten to twelve on the half equator. Between every three meshes is one short conical spine. Proportion of the major axis to the minor = 6 : 5. Minor axis equals three times the diameter of the inner spherical shell. Polar spines conical, thick, half as long as the major axis, thicker at the base than one pore. (This species differs from Stylatractus carduus only by the simple medullary shell.)