Page:Scientific results HMS Challenger vol 18 part 1.djvu/1040

832 3. Stauraspis furcata, n. sp.

Radial spines thin, quadrangular, prismatic; outer and inner halves nearly of equal length. The four apophyses of each spine simply forked (or partly with bifid fork-branches); each spine with eight to twelve sutural condyles. Meshes of the shell ten to twenty times as broad as the bars.

Dimensions.—Diameter of the shell 0.15; breadth of the spines and bars 0.003.

Habitat.—Central Pacific, Station 266, surface.

4. Stauraspis stauracantha, n. sp. (Pl. 137, figs. 5, 6).

Radial spines thin, in the inner longer half cylindrical, in the outer half conical with thickened base. Four apophyses of each spine doubly forked or dichotomously (more or less irregularly) branched; each spine with sixteen to twenty-four sutural condyles. Meshes of the shell of very different sizes and forms; the largest ten to fifteen, the smallest two to three times as broad as the bars.

Dimensions.—Diameter of the shell 0.14; breadth of of the spines 0.002 to 0.01, of the bars 0.002.

Habitat.—Tropical Atlantic, Station 343, surface.

Definition— without perforated plates; shell composed only of the meeting branches of the four crossed apophyses, which arise (opposite in pairs) from each radial spine. Condyles of the branch-ends bearing by-spines.

The genus Echinaspis exhibits the same structure of the shell as its ancestral form Stauraspis, and differs from it only in the development of by-spines on the sutural condyli.

1. Echinaspis dichotoma, n. sp.

Radial spines cylindrical, thin, outer half longer than the inner. Four apophyses of each spine simply forked (or partly with bifid fork-branches); therefore each spine usually possesses eight (sometimes ten to twelve) sutural condyles. Meshes of the shell ten to twelve times as broad as the bars. Each condyle bears a zigzag by-spine, half as long as the radius.

Dimensions.—Diameter of the shell 0.12, of the spines 0.004 to 0.006.

Habitat.—North Pacific, Station 253, surface.