Page:Scientific results HMS Challenger vol 18 part 2.djvu/460

1336 4. Dictyocodon prometheus, n. sp.

Shell tower-shaped, very similar to the preceding species in form and fenestration, but more slender and different in the longer and three-sided prismatic abdomen. Length of the three joints = 1 : 1 : 8, breadth = 1 : 3 : 7. Cephalis with two large divergent horns of three times the length, which are united by interior prolongations with the basal central point, from which arise the upper edges of the three divergent wings; the ends of the latter are directed downwards. Mouth with a corona of about thirty irregular, triangular feet.

Dimensions.—Length of the three joints, a 0.03, b 0.03, c 0.025; breadth, a 0.03, b 0.08, c 0.2.

Habitat.—Tropical Atlantic, Station 347, surface.

Definition.— (vel Tricyrtida triradiata aperta) without ribs in the thorax, but with three ribs enclosed in the abdomen, which are prolonged into three terminal feet.

The genus Pleuropodium, formerly confounded with Theopodium and Pterocanium, differs from these two closely allied ancestral genera in the localisation of the three lateral ribs, which have disappeared in the thorax and become limited to the abdomen. It is therefore intermediate between the former and the following Podocyrtis.

1. Pleuropodium charybdeum, Haeckel.

Pterocanium charybdeum, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 43, Taf. vi. figs. 7-10.

Podocyrtis charybdea, J. Müller, 1856, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 492.

Shell campanulate, armed with scattered, bristle-shaped spines, with sharp collar and slight lumbar stricture. Length of the three joints = 1 : 3 : 1, breadth = 1 : 4 : 5. Cephalis cupola-shaped, with a large prismatic, somewhat curved horn, half as long as the shell. Thorax hemispherical, spiny. Abdomen short and wide, three-sided prismatic, with three stout longitudinal ribs, which are prolonged into three slender, prismatic, nearly vertical, slightly curved feet, about as long as the shell. Pores irregular, roundish, of variable size.

Dimensions.—Length of the three joints, a 0.02, b 0.06, c 0.03; breadth, a 0.03, b 0.08, c 0.1.

Habitat.—Mediterranean (Messina, Nice, &c.), surface.

2. Pleuropodium cortina, n. sp.

Shell campanulate, smooth, with two distinct strictures. Length of the three joints = 1 : 4 : 2, breadth = 1 : 3 : 4. Cephalis subspherical, with a small, pyramidal, straight horn of the same length.