Page:Scientific results HMS Challenger vol 18 part 2.djvu/338

1214 4. Lamprodiscus lævis, Haeckel.

Eucecryphalus lævis, R. Hertwig, 1879, Organism. d. Radiol., p. 77, Taf. viii. figs. 6, 6a, 6b.

Shell smooth, with distinct collar stricture. Length of the two joints = 1 : 3, breadth = 1 : 6. Cephalis subspherical, with small circular pores and an oblique conical horn of twice the length. Thorax flat, pyramidal, twice as broad as long, with three strong, straight divergent edges and subregular roundish pores. Peristome smooth.

Dimensions.—Cephalis 0.025 diameter; thorax 0.08 long, 0.16 broad.

Habitat.—Mediterranean (Messina), R. Hertwig, surface.

Definition.— (vel Dicyrtida triradiata aperta) with three divergent lateral ribs in the wall of the flat conical or pyramidal thorax. Cephalis commonly with a horn. Peristome with a corona of spines.

The genus Lampromitra differs from the preceding and nearly allied Lamprodiscus only in the development of a dentated peristome, or an elegant corona of teeth around the wide open mouth. It bears therefore to the latter the same relation that Clathrocorona does to Clathrocanium.

1. Lampromitra coronata, n. sp. (Pl. 60, fig. 7, 7a).

Shell flat, conical, with slight collar stricture. Length of the two joints = 1 : 2, breadth = 2 : 7. Cephalis hemispherical, with a conical oblique horn of twice the length, and small subregular hexagonal pores. Thorax with larger, subregular, hexagonal meshes, six to eight times as broad as the bars. Peristome or basal margin of the thorax circular, with a marginal ring of smaller polygonal meshes and a triple coronal of short spines; two external rings of short conical centrifugal spines, and an internal ring of thin centripetal rods (fig. 7a). In fig. 7 the shell is seen from below and exhibits very distinctly the internal cross of the collar septum, composed of the four divergent cortinar bars; between the latter descend the four pear-shaped lobes of the central capsule (each containing an oil globule), whilst the apical part of the capsule (with the nucleus) is hidden in the large cap-shaped cephalis.

Dimensions.—Cephalis 0.03 long, 0.07 broad; thorax 0.06 long, 0.2 broad.

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

2. Lampromitra quadricuspis (Pl. 58, fig. 7).

Shell flat, conical, with sharp collar stricture. Length of the two joints = 1 : 3, breadth = 2 : 10. Cephalis hemispherical, with subregular circular pores and an oblique, conical, occipital horn of twice