Cortical shell thick walled, spiny, twice as broad as the medullary shell, with regular, circular pores, twice as broad as the bars; eight to ten on the half equator. Major polar spine about as long as the axis of the outer sphere, three-sided pyramidal; minor spine scarcely half as long, pommel-shaped, edged. (Similar in general form to Xiphatractus glyptodon, Pl. [17], figs. 9, 10; but differs in the simple medullary shell, the spherical form of both shells, and the simple circular regular pores.)
Dimensions.—Diameter of the outer sphere 0.12, pores 0.014, bars 0.007; inner sphere 0.06; length of the major spine 0.13, of the minor 0.05, greatest breadth 0.04.
Habitat.—Southern Pacific, surface, Station 289.
Subgenus 3. Sphærostylissa, Haeckel.
Definition.—Pores of the cortical shell irregular, of different size or form; surface smooth or a little rough.
6. Sphærostylus cottus, n. sp.
Cortical shell thick walled, smooth, about twice as broad as the medullary shell, with irregular, roundish pores, scarcely larger than the bars; fifteen to twenty on the half equator. Polar spines conical, the major once and a half to twice as long as the axis of the outer sphere, the minor scarcely as long as its radius.
Dimensions.—Diameter of the outer sphere 0.14, pores and bars 0.008 to 0.012; inner sphere 0.065; length of the major spine 0.2 to 0.3, of the minor 0.05 to 0.07, basal breadth 0.03.
Habitat.—Northern Atlantic, Færöe Channel, surface, John Murray.
7. Sphærostylus trigla, n. sp.