Page:Scientific results HMS Challenger vol 18 part 2.djvu/289

Rh and the other eighteen tertiary. Between them very numerous peripheral beams. Margin broad horizontal, reflexed like the brim of a "Bismarck" hat.

Dimensions.—Shell 0.17 long, 0.38 broad.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

Definition.— (vel Monocyrtida multiradiata aperta) with flatly conical, tent-shaped or nearly discoidal shell, and numerous branched radial beams.

The genus Cladarachnium differs from the preceding Litharachnium only in the ramification of the radial beams, the distal ends of which project over the margin of the shell. Only one species of the genus has been observed.

1. Cladarachnium ramosum, n. sp. (Pl. 55, figs. 5, 6).

Shell flatly conical or tent-shaped, with nearly straight lateral outlines; apical part somewhat higher. Apex with three cortinar pores surrounded by a few girdles of larger pores. From these there arise about twelve to fifteen strong radial beams at unequal distances; these are somewhat curved and irregularly branched. The network between them has irregular polygonal meshes and is more delicate towards the periphery. Margin with twenty-four to thirty irregular indentations or concave excisions, separated by the prominent distal ends of the branched ribs.

Dimensions.—Shell 0.16 long, 0.4 broad.

Habitat.—Central Pacific, Station 271, surface.

Definition.— (vel Monocyrtida multiradiata aperta) with ovate or urceolate shell and numerous radial ribs in its wall. Mouth more or less constricted, smooth, truncated. Apex without horn.

The genus Cystophormis, like the preceding genera, exhibits numerous prominent radial or longitudinal ribs in the wall of the urceolate shell; it differs from these in the constricted and truncated mouth, with smooth margin of the peristome.

1. Cystophormis pila, n. sp. (Pl. 52, fig. 1).

Shell balloon-shaped, subspherical, with twenty denticulate meridional ribs, alternating with twenty longitudinal rows of circular pores, which are twice as broad as the bars. Peristome constricted and then dilated, smooth, half as broad as the shell.

Dimensions.—Shell 0.11 long, 0.09 broad; mouth 0.06 broad.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.