Shell hemispherical, nearly twice as broad as long, smooth. Pores irregular, roundish, twice to four times as broad as the bars. Mouth wide open. Apical horn spindle-shaped, half as long as the shell. Three feet cylindrical, nearly straight and parallel, as long as the shell, forked at the distal end. (Exhibits an external similarity to Tripospyris semantis, Pl. [84], fig. 2, but has no trace of sagittal ring and constriction, and the simple shell-cavity has a wide open mouth.)
Dimensions.—0.06 long, 0.1 broad; horn 0.03 long, feet 0.07 long.
Habitat.—North Pacific, Station 241, depth 2300 fathoms.
9. Tripilidium cladopodium, n. sp.
Shell campanulate, rough, about as long as broad. Pores subregular, circular, as broad as the bars. Mouth slightly constricted. Apical horn and three divergent feet of nearly equal size and form, three-sided prismatic, straight and stout, irregularly dentate and branched, somewhat longer than the shell.
Dimensions.—Shell 0.08 diameter; horn and feet 0.1 to 0.12 long.
Habitat.—Central Pacific, Station 265, depth 2900 fathoms.
Genus 502. Tripodiscium,[[119]] Haeckel, 1881, Prodromus, p. 428.
Definition.—Archipilida (vel Monocyrtida triradiata aperta) without lateral ribs and apical horn, with three simple or branched terminal feet.
The genus Tripodiscium may be derived either from the preceding Tripilidium by loss of the apical horn, or from the nearly related Tristylospyris by loss of the sagittal ring and constriction. Some forms of the latter genus can scarcely be distinguished from similar species of the former.