Page:Scientific results HMS Challenger vol 18 part 2.djvu/383

Rh 7. Plectopyramis heteromma, n. sp.

Shell smooth, slenderly pyramidal, with concave outlines. Cephalis very small, subspherical, with a small oblique, conical horn, and very small, scarce circular pores. Thorax with nine stout concavely curved radial beams, which are connected by numerous (thirty to fifty or more) interrupted transverse bars. The large irregular meshes so produced are filled up by irregular, polygonal, delicate lattice-work.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax 0.6 long, 0.3 broad.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

8. Plectopyramis serrata, n. sp.

Shell thorny, slenderly pyramidal, with straight outlines. Cephalis very small, spherical, with a long oblique, conical horn, and very small circular pores. Thorax with nine stout, straight, regularly serrate ribs or radial beams, which are connected by numerous (twenty to thirty or more) interrupted transverse bars. The latter, being crossed by intercalated and interrupted irregular radial beams, produce a subregular secondary network of rectangular meshes of different sizes.

Dimensions.—Cephalis 0.02 long, 0.02 broad; thorax, 0.3 long, 0.2 broad.

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

9. Plectopyramis fenestrata, Haeckel.

Pyramis fenestrata, Bury, 1862, Polycystins of Barbados, pl. xxi. fig. 8.

Shell thorny, broadly pyramidal, with straight outlines. Cephalis very small, spherical, hyaline. Thorax with nine stout, spinulate, straight ribs or radial beams, which are connected by ten to fifteen transverse bars, which in the upper half are complete rings, in the lower half interrupted, and crossed by irregularly intercalated radial beams. Meshes therefore irregular, quadrangular. All the bars are thorny.

Dimensions.—Cephalis 0.01 diameter; thorax 0.2 long, 0.16 broad.

Habitat.—Tropical Atlantic.

10. Plectopyramis furcata, n. sp.

Shell spiny, slenderly pyramidal, with straight outlines. Cephalis small, spherical, with few small pores. Thorax with nine stout and straight spinulate ribs, which are connected by a variable number of irregular interrupted transverse bars; the large quadrangular meshes so produced are filled up by irregular delicate network. The entire surface of the thorax is covered with short forked spines.

Dimensions.—Cephalis 0.02 diameter; thorax 0.3 long, 0.2 broad.

Habitat.—Indian Ocean (Zanzibar), Pullen, depth 2200 fathoms.