Page:Scientific results HMS Challenger vol 18 part 2.djvu/365

Rh meshes, closing also the basal mouth. (In fig. 5 the greater part of the web is taken off to demonstrate the large holes of the thorax). Only two feet are visible.

Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.09 long, 0.12 broad.

Habitat.—Central Pacific, Station 274, surface.

2. Clathrolychnus periplectus, n. sp. (Pl. 64, fig. 6).

Cephalis subspherical, with subregular, circular pores and a pyramidal horn of the same length. Length of the two joints = 1 : 2, breadth = 1 : 3. Thorax with three large elliptical holes between the three pyramidal, divergent feet, which are connected at the distal end by a broad band of network, composed of five to ten rows of polygonal pores. The entire pyramidal shell is enveloped by a very delicate web, which on the sides is composed of subregular, square meshes, and on the closed mouth of polygonal meshes. (In fig. 6 only a part of the web is represented.)

Dimensions.—0.04 long, 0.05 broad; thorax 0.08 long, 0.14 broad.

Habitat..—Central Pacific, Station 271, surface.

Sethophormida et Sethophænida, Haeckel, 1881, Prodromus, p. 432, 433.

Definition.— multiradiata. ( with a two-jointed shell, divided by a transverse constriction into cephalis and thorax, and bearing numerous—four to nine or more—radial apophyses.)

The family, composed of the Sethophormida and Sethophænida of my Prodromus, comprises those in which the shell is two-jointed and bears numerous radial apophyses. The two subfamilies differ in the shape of the mouth, which in the Sethophormida is a simple, wide opening; in the Sethophænida closed by a lattice-plate.

Numerous fossil and living forms of Anthocyrtida were described formerly by Ehrenberg in his genera Carpocanium and Anthocyrtis. These, however, represent only a small part of the whole family, which exhibits a great variety in the composition of the lattice-work and in the number of radial beams. The number of species here described amounts to one hundred and forty, and these are disposed in fourteen genera (twelve Sethophormida and two Sethophænida).

The Sethophormida may be again divided into two different groups or tribes, the Sethamphorida and Carpocanida; in the former the thorax bears numerous radial ribs, enclosed in its wall; in the latter these ribs have disappeared, and only a corona of terminal feet is developed around the mouth. The shell of the former is usually pyramidal, with a widely open mouth; of the latter ovate, with a constricted mouth. The mouth of the thorax becomes perfectly closed in the Sethophænida.