Page:Scientific results HMS Challenger vol 18 part 2.djvu/261

Rh 5. Tripocalpis cortinaris, n. sp. (Pl. 97, fig. 3).

Shell hemispherical, one and a half times as broad as long, with regular, circular, hexagonally framed pores, Apical horn stout, three-sided pyramidal, with three serrate edges. From the base of the latter arise three strongly dentate and curved lateral ribs, with recurved teeth, and these are prolonged into the serrate convex edge of the three basal feet, which are crescentic and twice as long as the shell.

Dimensions.—Shell 0.07 long, 0.1 broad; horn 0.06 long, feet 0.14 long.

Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.

Definition.— (vel Monocyrtida triradiata aperta) with three lateral ribs prolonged into three terminal feet. Apex without horn.

The genus Tripodonium differs from the preceding Tripocalpis, its probable ancestral form, only in the loss of the apical horn (already very small in some forms of the latter). It bears therefore to the latter the same relation that Sethopilium does to Dictyophimus.

1. Tripodonium campanulatum, n. sp.

Shell campanulate, somewhat broader than high, with regular circular pores, twice as broad as the bars. Three broad lateral wings, lamellar, triangular, are prolonged over the peristome into three short triangular lamellar feet one-fourth as long as the shell.

Dimensions.—Shell 0.08 long, 0.09 broad; feet 0.02 long.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

2. Tripodonium ovatum, n. sp.

Shell ovate, one and one-third times as long as broad, with numerous and small circular pores, scarcely as broad as the bars. Three prominent longitudinal ribs, arising in the lower half of the shell-wall, are prolonged into three divergent conical curved feet, about half as long as the shell.

Dimensions.—Shell 0.12 long, 0.09 broad; feet 0.06 long.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

Definition.— (vel Monocyrtida triradiata aperta) with three lateral wings and a peristomial corona of numerous terminal feet. Shell ovate, with constricted mouth, without apical horn.