Page:Scientific results HMS Challenger vol 18 part 2.djvu/269

Rh

Definition.— (vel Monocyrtida triradiata aperta) with three latticed terminal feet. Shell ovate or subconical, with an apical horn.

The genus Tridictyopus differs from the nearly allied Tripilidium in the possession of three large fenestrated shovel-shaped feet, forming direct prolongations of the large conical shell. The lattice work exhibits a peculiar elegant structure recurring in the similar, perhaps nearly related, Cephalospyris (Pl. 83, fig. 10; Pl. 96, fig. 28). The central capsule is large, ellipsoidal or ovate, and fills up the greater part of the shell cavity (compare R. Hertwig, 1879, loc. cit., p. 75).

1. Tridictyopus vatillum, n. sp. (Pl. 51, fig. 8).

Shell campanulate, about as long as broad (excluding horn and feet). Pores irregular, polygonal, in the middle part more regular, triangular. Horn short and stout, three-sided pyramidal. Three feet large, triangular, shovel-shaped, about half as long as the shell.

Dimensions.—Shell 0.14 long, 0.15 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

2. Tridictyopus conulus, n. sp. (Pl. 51, fig. 7).

Shell campanulate conical, about one and a half times as long as broad (excluding horn and feet). Pores mostly triangular, disposed in subregular hexagonal figures, which are separated by bands of smaller irregular polygonal pores. Horn short and stout, three-sided pyramidal. Three feet triangular shovel-shaped, convergent, about one-sixth as long as the shell.

Dimensions.—Shell 0.3 long, 0.2 broad; horn 0.04 long, feet 0.05 long.

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

3. Tridictyopus elegans, R. Hertwig.

Tridictyopus elegans, R. Hertwig, 1879, Organismus d. Radiol., p. 75, Taf. vii. fig. 3, 3a, 3b.

Shell slender, conical, campanulate, about twice as long as broad (excluding horn and feet). Most pores subregular triangular, with some irregular polygonal ones intermingled. The horn in the two observed specimens was broken off, together with the conical apex of the shell. Three feet triangular shovel-shaped, about one-sixth as long as the shell.

Dimensions.—Shell 0.3 long, 0.15 broad; feet 0.05 long.

Habitat.—Mediterranean (Messina), R. Hertwig, surface.