12. Challengeria havergalli, John Murray.
Shell subspherical, slightly compressed. Peristome semitubular, slender, somewhat curved, in the lower half a simple half-cylinder, in the upper half forked, with two divergent teeth, nearly as long as the shell.
Dimensions.—Diameter of the shell 0.1 to 0.15, length of the peristome 0.08 to 0.12.
Habitat.—South Pacific, Station 300, depth 1375 fathoms.
13. Challengeria elephas, n. sp.
Shell ellipsoidal, not compressed. Peristome very similar to that of Challengeron diodon (Pl. 99, fig. 6), from which this species differs mainly in the absence of an apical spine, and in a more constricted mouth. The two conical teeth of the mouth are very large, nearly as long as the shell, straight, and almost parallel, each tooth has a large hole on the thickened base.
Dimensions.—Diameter of the shell 0.22, length of the teeth 0.2.
Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.
Subgenus 3. Challengerilla, Haeckel.
Definition.—Peristome with three teeth or trifid, with an odd dorsal and two paired lateral teeth (Challengeriæ triodontes).
14. Challengeria macleari, John Murray.
Shell subcircular, lenticular, with a sharp marginal edge. Peristome semitubular, an oblique half-cylinder, with three divergent, short, triangular teeth; the dorsal odd tooth nearly vertical, the paired lateral teeth subhorizontal. Length of the peristome about one-third or one-fourth of the diameter of the shell.
Dimensions.—Diameter of the shell 0.25 to 0.35, length of the peristome 0.1 to 0.12.
Habitat.—South Atlantic, Stations 325 to 332, depth 1715 to 2900 fathoms.
15. Challengeria tridens, n. sp.
Shell subspherical, slightly compressed. Peristome about as long as the radius of the shell, with three diverging and obliquely descending teeth; the dorsal odd tooth twice as long as the paired lateral teeth.
Dimensions.—Diameter of the shell 0.08 to 0.12, length of the peristome 0.05 to 0.07.
Habitat.—North Atlantic, Færöe Channel (Gulf Stream), John Murray.
