Page:Scientific results HMS Challenger vol 18 part 1.djvu/1024

816 each suture. Both aspinal meshes kidney-shaped, four times as broad as the small sutural meshes. Radial spines thick, in the inner longer part cylindrical, in the outer shorter part conical. (Differs from all other species in the multiplication of the sutural pores.)

Dimensions.—Diameter of the shell 0.2, of the aspinal pores 0.016, of the sutural pores 0.004.

Habitat.—Equatorial Atlantic, Station 347, surface.

Definition.— with twenty plates, which are perforated by forty aspinal pores (two pores in each plate). Surface of the shell without combs and dimples, but armed with numerous by-spines.

The genus Diporaspis has the same characteristic structure of the shell as the typical Dorataspis, and differs from it only in the development of numerous by-spines on the surface. The number of the sutures between the twenty plates is sometimes fifty-two, at other times fifty-four, and in each suture we find occasionally a single pore, at other times two or three such pores.

Definition.—Shell with fifty-two sutures, four polar plates on each pole of the main axis meeting in one common point; therefore all eight polar plates pentagonal and of equal size. Shell therefore composed of four (equatorial) hexagonal plates, and of sixteen pentagonal (eight tropical and eight polar) plates.

1. Diporaspis nephropora, n. sp. (Pl. 134, fig. 15).

Shell with fifty-two sutures and fifty-two sutural pores, with four hexagonal and sixteen pentagonal plates. Both aspinal pores of each plate kidney-shaped, about twice as broad as the circular sutural pores. Radial spines thin, cylindrical, longer than the radius. By-spines forked, only one-third as long as the radius.

Dimensions.—Diameter of the shell 0.13, parmal pores 0.03, sutural pores 0.07.

Habitat.—North Pacific, Station 244, surface.

2. Diporaspis circopora, n. sp.

Shell with fifty-two sutures and one hundred to one hundred and fifty sutural pores, with four hexagonal and sixteen pentagonal plates. Both aspinal pores of each plate circular, very large, six to eight times as broad as the small circular sutural pores (in each suture two to three pores).