Page:Scientific results HMS Challenger vol 18 part 2.djvu/380

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Definition.—Pyramidal shell with twelve or more radial beams (commonly twelve to twenty-four, sometimes forty or more).

10. Sethopyramis dodecalactis, n. sp.

Shell smooth, slender, pyramidal. Cephalis small, spherical, hyaline, with a short conical horn. Thorax with twelve radial ribs in the upper half, between which twelve others are interpolated in the lower half. These are connected by twenty to twenty-four complete transverse rings. The meshes so produced are subregular, rectangular.

Dimensions.—Cephalis 0.03 diameter; thorax 0.6 long, 0.2 broad.

Habitat.—Indian Ocean, Madagascar (Rabbe), surface.

11. Sethopyramis bicornis, n. sp.

Shell spiny, slender, pyramidal. Cephalis small, spherical, hyaline, with two divergent conical horns, the major (occipital) three times and the minor (frontal) twice as long. Thorax slender, pyramidal, campanulate, thorny, with twenty to thirty radial beams, which are little curved, convex in the upper, concave in the lower half, and connected by numerous interrupted transverse bars. Meshes in the upper third rounded, in the lower two-thirds quadrangular, of very different sizes. Surface covered with spinules.

Dimensions.—Cephalis 0.02 diameter; thorns 0.9 long, 0.4 broad.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

12. Sethopyramis maxima, n. sp.

Shell smooth, slender, pyramidal. Cephalis small, spherical, with few small pores, and a stout, vertical, conical horn twice the length. Thorax very prolonged, conical, with straight lateral outlines and numerous (twenty to fifty) radial beams (in the upper third twelve, in the middle third twenty-four, in the lower third forty to fifty, by interpolation); they are connected by very numerous interrupted transverse bars. Meshes subregular, quadrangular. Surface smooth.

Dimensions.—Cephalis 0.02 diameter; thorax 1.05 long, 0.45 broad.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Definition.— (vel Dicyrtida multiradiata aperta) with numerous straight or slightly curved radial ribs in the wall of the pyramidal thorax. Network double, the large primary meshes being fenestrated by fine secondary network. Cephalis commonly without horn.