Page:Scientific results HMS Challenger vol 18 part 2.djvu/111

Rh

Definition.—Sagittal ring circular, smaller than the other two rings, which are both elliptical.

1. Trissocyclus stauroporus, n. sp. (Pl. 83, fig. 5).

Sagittal ring circular, smaller than the other two equal elliptical rings. On each of the six corners (or crossing points of every two rings) are developed four small pores, forming a cross around the poles of the three axes. All three rings smooth, without spines.

Dimensions.—Height of the frontal ring 0.09, breadth 0.13.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

2. Trissocyclus triaxonius, n. sp.

Sagittal ring circular, smaller than the two other equal elliptical rings. From the edges of all three rings are developed small branches, which by irregular ramification and anastomoses form small irregular meshes along the rings. Similar to Trissocircus octostoma, but with thicker rings; it may be developed from the latter species by connection of the branches which border the rings.

Dimensions.—Height of the frontal ring 0.12, breadth 0.15.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

Definition.—All three rings equal, circular.

3. Trissocyclus sphæridium, n. sp. (Pl. 93, fig. 12).

All three rings equal, circular, thorny; their rods prismatic, three-sided, with three denticulate edges; the teeth of the lateral edges become branched, and form by anastomoses of the branches small irregular meshes, which partly protect the eight large open gates.

Dimensions.—Diameter of the three rings 0.16, thickness 0.012.

Habitat.—Indian Ocean, Belligemma, Ceylon (Haeckel), surface

Parastephida, Haeckel, 1881, Prodromus, p. 446.

Definition.— with two parallel horizontal rings, an upper mitral and a lower basal ring; both connected by complete or incomplete vertical rings, or by parallel vertical columellæ.