Page:Scientific results HMS Challenger vol 18 part 2.djvu/784

1660 divergent teeth; the terminal teeth are the halves of a forked dorsal tooth and diverge laterally; the lower teeth are nearly horizontal and directed ventrally.

Dimensions.—Diameter of the shell 0.13 to 0.15; length of the peristome 0.07 to 0.1.

Habitat.—Tropical Pacific, Stations 274 to 276, depth 2350 to 2750 fathoms.

25. Challengeron wyvillei, n. sp. (Pl. 99, fig. 15).

Shell ovate, lenticular, strongly compressed, with numerous (forty to fifty) short, conical, radial spines on the margin; the spines are larger on the aboral side and spinulate. Peristome narrow, with two parallel, lateral, lamellar, forked teeth, about as long as the radius; the upper branch of the forks is sabre-shaped, obliquely truncate, subvertical, ciliate, and much broader than the lower nearly horizontal branch, which is directed towards the ventral side and curved upwards.

Dimensions.—Length of the shell 0.12 to 0.16, breadth 0.1 to 0.14; length of the peristome 0.08 to 0.11.

Habitat.—Tropical Atlantic, Station 347, depth 2250 fathoms.

Definition.— with a pharynx, or an internal prominent mouth tube.

Definition.— with a pharynx, without teeth on the mouth, and without marginal spines.

The genus Entocannula and the two following genera represent together the subfamily Pharyngellida, differing from the preceding Lithogromida in the development of a peculiar pharynx, an internal, cylindrical, or funnel-shaped tube, which is conspicuous, leads from the mouth into the shell-cavity, and is provided with an inner and an outer opening. The Pharyngellida are much rarer than the Lithogromida; only ten species have been observed of the former, fifty of the latter. Entocannula is the simplest form of the Pharyngellida, having a smooth shell, without aboral teeth and marginal spines; it differs from Lithogromia only in the possession of the pharynx. One remarkable species is covered entirely with extremely thin, flinty hairs, and may represent therefore a peculiar genus, Trichogromia.