Page:Scientific results HMS Challenger vol 18 part 1.djvu/1074

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Definition.— with forty parmal pores (two on each plate), with numerous by-spines and with a network of prominent crests on the dimpled surface.

The genus Coleaspis differs from its ancestral genus Dictyaspis in the development of numerous by-spines, and bears therefore among the ellipsoidal Belonaspida the same relation to it as Hystrichaspis does to Coscinaspis among the spherical Dorataspida. If the four equatorial spines in Coleaspis become different in pairs, it passes over into Hexalaspis. The shell is usually very dark and thick-walled.

1. Coleaspis coronata, n. sp.

All twenty spines of nearly equal size and form, about as long as the radius of the shell, compressed, sword-like, two-edged; both equatorial spines of the hydrotomical axis little longer than the eighteen others. Crests between the dimples of the shell-surface dentated, forming around the basal half of each spine a cylindrical sheath with a dentated, crown-like mouth, the teeth of which are prolonged into simple by-spines. (Similar to Hexaconus coronatus, Pl. 139, fig. 5, but differing in the nearly equal size of the spines and their sheaths, and in the longer by-spines.)

Dimensions.—Major axis of the shell 0.2, minor 0.17; length of the spines 0.12, basal breadth 0.02.

Habitat.—Central Pacific, Station 266, surface.

2. Coleaspis vaginata, n. sp. (Pl. 140, fig. 13).

All twenty spines of nearly equal size and form, nearly as long as the diameter of the shell, conical; both equatorial spines of the hydrotomical axis about one-third longer than the eighteen others. Crests between the dimples of the shell-surface serrated, forming around the basal half of each spine a conical truncate sheath with crested surface and serrated mouth, the teeth of which are prolonged into short by-spines. (Similar to Hexaconus vaginatus, Pl. 139, fig. 7, but differing in the nearly equal size of all the spines and in the double thickness of the shell-wall.)

Dimensions.—Major axis of the shell 0.12, minor 0.1, length of the spines 0.08, basal breadth 0.01.

Habitat.—North Pacific, Station 253, surface.

3. Coleaspis obscura, n. sp.

All twenty spines of nearly equal size and form, little longer than their large cylindrical sheaths, which are nearly as long as the radius of the shell, and armed on the truncated mouth with strong triangular by-spines, both equatorial spines of the hydrotomical axis one and a half times as long as the eighteen others. Shell very dark and thick walled, quite opaque.