Habitat.—Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms.
Subgenus 2. Tholonilla, Haeckel.
Definition.—Surface of the outer shell covered with radial spines or thorns.
4. Tholonium hexonium, n. sp. (Pl. [10], fig. 17).
Outer shell ellipsoidal, without dome-shaped protuberances, covered with numerous (thirty to fifty) thin and long, bristle-shaped radial spines; network very delicate, irregular, with roundish pores. Inner shell with six marked hemispherical domes of somewhat different sizes; pores regular, circular, with prominent hexagonal frames, twice as broad as the bars; ten to twelve on the basal semicircle of one cupola.
Dimensions.—Major axis of the outer shell 0.15, minor axis 0.14; major axis of the inner shell 0.13, minor axis 0.12; pores 0.008, bars 0.004.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
5. Tholonium sphæronium, n. sp.
Outer shell very thin walled, spherical, without dome-shaped protuberances, with smooth surface, excepting eight large radial spines, rising from the eight corners of the inner cubical central chamber. Pores of the outer shell very small, subcircular. Inner shell very thick walled, with six marked hemispherical domes; pores subregular, circular, with prominent hexagonal frames, twice as broad as the bars; six to eight on the semicircle of one cupola.
Dimensions.—Diameter of the spherical outer shell 0.15, inner shell 0.11; pores of the inner 0.01, bars 0.005.