Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.
2. Amphistylus hippocampus, n. sp.
Radial proportion of the three spheres = 3 : 2 : 1. Cortical shell thick walled, smooth; its pores regular, circular, hexagonally lobed, three times as broad as the bars; twelve to fifteen on the half equator. Major polar spine three-sided pyramidal, about as long as the axis of cortical shell; minor spine pommel-like, edged, scarcely one-third as long. (Similar to Sphærostylus hippocampus, Pl. [16], figs. 10, 11, but differs in the larger size, the double medullary shell, and the straight, not curved, major spine.)
Dimensions.—Diameter of the outer sphere 0.11, middle 0.07, inner 0.035; pores of the outer shell 0.011, bars 0.004; length of the major spine 0.12, of the minor 0.04, breadth 0.03.
Habitat.—North Pacific, Station 244, depth 2900 fathoms.
3. Amphistylus glyptodon, n. sp.
Radial proportion of the three spheres = 6 : 3 : 1. Cortical shell thick walled, spiny, with irregular, roundish pores, two to four times as broad as the bars; ten to twelve on the half equator. Inner aperture of each pore closed by a thin fenestrated lamella with five to seven small pores. Major polar spine three-sided pyramidal, longer than the diameter of the outer sphere; minor polar spine scarcely as long as its radius, pommel-shaped. (Similar to Xiphatractus glyptodon, Pl. [17], figs. 9, 10, but differs in the spherical, not ellipsoidal, form of the three shells and the size of the polar spines.)
Dimensions.—Diameter of the outer sphere 0.12, middle 0.06, inner 0.02; pores and spines of the outer shell 0.01 to 0.02, bars and porules 0.006; length of the major polar spine 0.15, of the minor 0.05, breadth 0.04.
Habitat.—South Pacific, Station 285, depth 2375 fathoms.