Dimensions.—Length of the shell 3.2, breadth 1.6.
Habitat.—North Pacific, Station 250, depth 3050 fathoms.
2. Tuscaridium lithornithium, n. sp. (Pl. [100], figs. 8, 8a, 8b).
Shell spindle-shaped, twice as long as broad, very similar to the preceding closely allied species. It differs from the latter in the following characters:—The curved proboscis of the peristome is broader and more spiny. The four radial tubes of the mouth and the terminal caudal spine are very spiny (in the preceding species nearly smooth). The number of buccal holes (six to eight on each side of the mouth) is twice as great as in the former. Each circoral tube is pierced at the base by six or eight (in the former by four pores), and the base of the caudal spine exhibits a cross of four pores (in Tuscaridium cygneum only two pores).
Dimensions.—Length of the shell 3.6, breadth 1.8.
Habitat.—North Pacific, Station 264, depth 3000 fathoms.
Order IV. PHÆOCONCHIA, Haeckel, 1879.
Definition.—Phæodaria with a bivalved lattice-shell, composed of two free opposite valves (a dorsal and a ventral), between which the central capsule is enclosed.