Page:Scientific results HMS Challenger vol 18 part 2.djvu/279

Rh 6. Peridium alatum, n. sp. (Pl. 97, fig. 7).

Shell subspherical smooth, with regular circular, hexagonally-framed pores. Basal plate with nine pores (three larger central and six smaller distal pores). Horn apical, of equal size and the same form as the three feet, three-sided prismatic, with three broad prominent wings, somewhat longer than the shell.

Dimensions.—Shell 0.07 long, 0.08 broad; horn and feet 0.1 to 0.12 long.

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

7. Peridium cervinum, n. sp.

Shell subspherical, spiny, with subregular circular pores. Basal plate with four pores (?). Horn apical, conical, about as long as the shell. Feet three to four times as long, cylindrical curved, with irregular simple or forked branches like the antlers of a deer.

Dimensions.—Shell diameter 0.1, horn 0.1 long, feet 0.3 to 0.4 long.

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

Definition.— (vel Monocyrtida triradiata clausa) without internal columella, with two or more apical horns.

The genus Archipera differs from the preceding Peridium only in the multiplication of the apical horn, which in the latter is always simple. The number of horns is usually two or three, sometimes four or more. The species bearing three horns may be derived directly from Triceraspyris by loss of the sagittal ring.

1. Archipera cortiniscus, n. sp. (Pl. 98, fig. 5).

Shell ovate, thorny, with large roundish pores, which are closed by sieve-plates with numerous small porules. Basal plate with two pairs of simple large pores (two smaller jugular and two larger cardinal, similar to Pl. 98, fig. 10b). Two horns divergent, curved, slender, pyramidal; the apical horn longer than the shell, the frontal horn shorter. Three feet divergent, longer than the shell, three-sided prismatic, at the distal end club-shaped, thorny.

Dimensions.—Shell 0.1 long, 0.08 broad; horns and feet 0.11 to 0.14 long.

Habitat.—Tropical Pacific, Station 225, depth 4475 fathoms.

2. Archipera pentacantha, n. sp.

Shell pear-shaped, smooth, with numerous and small irregular roundish pores. Basal plate with three larger pores. Two horns and three feet of nearly equal size and similar form, three-sided