Page:Scientific results HMS Challenger vol 18 part 2.djvu/379

Rh Thorax broad, pyramidal, with slightly concave lateral outlines and nine (sometimes eight or ten) curved ribs, which are connected by eighteen to twenty-four complete transverse rings. The large meshes, so produced, have the form of a parallel trapezoid, and are in the eighth transverse row three times as broad as long. (Differs from Bathropyramis trapezoides, Pl. 54, fig. 3, mainly by the possession of a well developed cephalis).

Dimensions.—Cephalis 0.04 long, 0.03 broad; thorax (with eighteen rings) 0.32 long, 0.24 broad.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

7. Sethopyramis spinosa, n. sp.

Shell thorny, slender, pyramidal. Cephalis small, subspherical, with few small pores and a straight, vertical, conical horn twice the length. Thorax with nine straight ribs, which are connected by sixteen to twenty complete transverse nine-angled rings. The large meshes so produced are subregular, square. From each nodal point a short conical spine arises. (Differs from the similar Bathropyramis spinosa, Pl. 54, fig. 4, by the development of the cephalis and the simple pointed, unforked spines.)

Dimensions.—Cephalis 0.03 diameter; thorax (with sixteen rings) 0.2 long, 0.12 broad.

Habitat.—Central Pacific, Station 263, depth 2650 fathoms.

8. Sethopyramis hexagonalis, n. sp.

Shell papillate, slender, pyramidal. Cephalis small, hemispherical, with a straight conical horn twice the length, and small circular pores. Thorax conical, with slightly convex outlines and nine stout, somewhat curved ribs in zig-zag form, which are connected by ten to twelve interrupted transverse bars. From each nodal point a small conical papilla arises. The large meshes so produced are regular, hexagonal, gradually increasing in size towards the mouth.

Dimensions.—Cephalis 0.03 diameter; thorax (with twelve transverse rows of meshes) 0.18 long, 0.12 broad.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

9. Sethopyramis cyclomma, n. sp.

Shell thorny, slender, pyramidal. Cephalis large, subspherical, with numerous very small circular pores, and a small conical horn of the same length. Thorax similar in form and structure to that of the preceding species; but each hexagonal mesh is provided with a very thin circular hyaline ring (like a diaphragm), so that the openings are not hexagonal, but circular. From each nodal point a short pointed conical or slightly forked spine arises.

Dimensions.—Cephalis 0.02 diameter; thorax (with ten transverse rows of meshes) 0.18 long, 0.14 broad.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.