Page:Scientific results HMS Challenger vol 18 part 1.djvu/1033

Rh Crests between the dimples armed with long forked by-spines with divergent fork-branches. Radial spines cylindrical, very long and thick, longer than the diameter of the shell.

Dimensions.—Diameter of the shell 0.14, aspinal pores 0.08, sutural pores 0.03.

Habitat.—Central Pacific, Station 266, surface.

9. Hystrichaspis fruticata, n. sp. (Pl. 138, fig, 7).

Shell with numerous (one hundred and fifty to two hundred?) funnel-shaped dimples, the majority of which are blind, the minority perforated; forty aspinal pores elliptical, of the same size as the circular sutural pores. Crests between the dimples bearing elegant arborescent by-spines. Twenty radial main-spines long and thin, cylindrical or a little compressed.

Dimensions.—Diameter of the shell 0.17, pores 0.01.

Habitat.—Tropical Pacific, Station 275, surface.

10. Hystrichaspis serrata, n. sp.

Shell with numerous (two hundred to three hundred?) funnel-shaped dimples, the majority of which are blind, the minority perforated; forty aspinal pores of the same size as the sutural pores. Crests between the dimples covered with denticulated by-spines. Twenty radial main-spines compressed, two-edged, with serrated edges, about as long as the diameter of the shell.

Dimensions.—Diameter of the shell 0.21, pores 0.012.

Habitat.—North Pacific, Station 238, surface.

Definition.— with twenty plates, which are perforated by eighty to two hundred or more parmal pores (two aspinal and two to ten or more coronal pores in each plate). Surface without by-spines.

The genus Coscinaspis, together with the following nearly allied genus Acontaspis, may be separated from the other Ceriaspida as a peculiar tribe, Coscinaspida. This tribe is characterised by the larger number of the parmal pores. Whilst in all other Ceriaspida this number is constantly forty (only two pores in each plate), here it may be from eighty to two hundred or more; in each shield the two primary "aspinal pores" are surrounded by a circle of two to ten or more (commonly eight to twelve) "coronal pores." The number of sutural pores in this group is also usually larger.