Dimensions.—Diameter of the shell 0.24 to 0.28.
Habitat.—Central Pacific, Stations 270 to 274, surface, and at various depths.
2. Conchidium thecidium, n. sp. (Pl. [124], fig. 6).
Shell subspherical, slightly compressed on both sides. Dorsal valve somewhat smaller than the ventral, of similar form. Principal axis of the shell somewhat longer than the sagittal, and this longer than the frontal axis. Margins of the valves smooth in the oral quarter, strongly dentate in the remainder; on each side of one valve eight or nine very large triangular teeth, half as long as the height of the valve. Aboral hinge with two unequal, stout, four-sided pyramidal horns; the dorsal horn half as long at the ventral. Mouth with two unequal lips, the upper shorter than the lower. Pores of the shell subregular, hexagonal, three to four times as broad as the bars. The figured specimen, well preserved, contained in the central capsule two nuclei, one in the dorsal, the other in the ventral half.
Dimensions.—Length of the shell 0.28 to 0.33, height 0.27 to 0.3, breadth 0.22 to 0.24.
Habitat.—South Pacific, Station 292, depth 1600 fathoms.
3. Conchidium rhynchonella, n. sp. (Pl. [124], fig. 3).
Shell with three different dimensive axes in the proportion = 6 : 5 : 4. Ventral valve semi-ovate, larger than the humpbacked dorsal valve. Margins of the valves dentate almost in the whole periphery; on each side of one valve twelve or thirteen strong conical teeth. Aboral hinge with two very unequal horns, the dorsal much smaller than the pyramidal ventral. Under lip of the mouth emarginate, much larger than the acute upper lip. Pores subregular, circular, twice as broad as the bars.
Dimensions.—Length of the shell 0.3, height 0.25, breadth 0.2.
Habitat.—North Pacific, Stations 244 to 253, surface, and at various depths.