Dimensions.—Major axis 0.16, minor axis 0.13; pores 0.007, bars 0.01; main axes of both ellipsoidal medullary shells 0.09 and 0.04; length and basal breadth of the polar spines 0.04 to 0.05.
Habitat.—Pacific, central area, Stations 270 to 272, depth 2425 to 2925 fathoms.
Subgenus 2. Stylatractylis, Haeckel.
Definition.—Network of the outer shell regular, with meshes of equal size and similar form; surface thorny or papillose, covered with small spinules or tubercles.
4. Stylatractus giganteus, n. sp. (Pl. [17], fig. 1).
Amphistylus giganteus, Haeckel, 1879, Atlas (pl. xvii. fig. 1).
Cortical shell papillose, very thick walled, with regular network; pores circular, with double margin, about twice as broad as the bars; ten to twelve on the half equator. The cortical shell is connected with the outer medullary shell by numerous strong beams, and the inner prolongations of both polar spines are much stronger. The circular pores of the outer medullary shell are three times as large as those of the inner, and equal to those of the cortical shell, but the bars are much thinner. Polar spines very strong, three-sided pyramidal, with spirally contorted edges, as long as the main axis, as broad at the base as the inner medullary shell.
Dimensions.—Major axis of the cortical shell 0.3, minor axis 0.22; pores 0.02, bars 0.01; main axes of the ellipsoidal medullary shells 0.14 and 0.07; length of the polar spines 0.3, basal thickness 0.06.
Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.
5. Stylatractus carduus, Haeckel.