2. Lithopera bursella, Ehrenberg.
Lithopera bursella, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 297, Taf. x. fig. 4.
Shell of about the same form and structure as in the nearly allied preceding species, but smaller, of more slender form, with smaller pores and thinner bars. Length of the two joints = 1 : 5, breadth = 1 : 3. In the specimen observed by me the three internal, divergent bars of the ellipsoidal thorax (not seen by Ehrenberg) were as distinct as in the similar preceding and following species.
Dimensions.—Cephalis 0.02 diameter; thorax 0.1 long, 0.06 broad.
Habitat.—Indian Ocean, Zanzibar (Pullen), Madagascar (Rabbe), surface.
3. Lithopera ananassa, n. sp. (Pl. [57], fig. 3).
Shell of about the same form and structure as in the two preceding species, but larger and more robust, and differing in the spiny surface. Length of the two joints = 1 : 5, breadth = 1 : 4. Here also the lower half of the spherical cephalis is submerged in the ellipsoidal thorax, and from the collar stricture arise three strong, internal, divergent beams. The bars of the hexagonal pores are much thicker than in the two preceding species.
Dimensions.—Cephalis 0.03 diameter; thorax 0.16 long, 0.12 broad.
Habitat.—Tropical Atlantic, Stations 347 to 352, surface.
4. Lithopera globosa, n. sp.