Habitat.—Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms.
2. Challengeron cochlear, n. sp.
Shell nearly circular, lenticular, strongly compressed, with a single straight conical spine on the apical pole, about half as long as the radius. Peristome spoon-shaped, obliquely curved and inclined over the mouth, with a single terminal tooth, somewhat longer than the radius.
Dimensions.—Diameter of the shell 0.1, length of the peristome 0.06.
Habitat.—Indian Ocean, Cocos Islands, Rabbe, surface.
3. Challengeron diodon, n. sp. (Pl. [99], fig. 6).
Shell ovate, slightly compressed, with a single straight conical spine on the aboral pole, half as long as the radius. Peristome short and broad, collar-shaped, about twice as broad as long, and half as long as the radius, obliquely inclined over the mouth, with two divergent straight teeth, which are conical and longer than the shell-radius; beyond each tooth a large ovate hole in the wall of the peristome.
Dimensions.—Diameter of the shell 0.08 to 0.1, length of the teeth 0.06 to 0.08.
Habitat.—South-Eastern Pacific, Station 298, depth 2225 fathoms.
4. Challengeron pearceyi, n. sp. (Pl. [99], fig. 7).