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.
Genus 498. Tripterocalpis,[[115]] Haeckel, 1881, Prodromus, p. 428.
Definition.—Archipilida (vel Monocyrtida triradiata aperta) with three lateral wings and a peristomial corona of numerous terminal feet. Shell ovate, with constricted mouth, without apical horn.
The genus Tripterocalpis is distinguished from the other Archipilida by the remarkable combination of three lateral wings and of numerous (six to nine or more) terminal feet. It may be derived directly from the preceding Tripocalpis by multiplication of the terminal feet. These are sometimes obliquely directed. The central capsule is ellipsoidal or ovate, and fills up the greater part of the shell.
1. Tripterocalpis phylloptera, n. sp. (Pl. [51], fig. 1).
Shell slender, ovate, nearly twice as long as broad. Pores circular, of different sizes and at unequal distances. Along the lower half of the shell there arise three broad triangular lamellar wings. Peristome with twelve conical, nearly parallel and vertical feet, about one-sixth as long as the shell.
Dimensions.—Shell 0.2 long, 0.12 broad; wings 0.1 long, feet 0.03 long.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.