Page:Scientific results HMS Challenger vol 18 part 2.djvu/97

Rh 1. Zygostephanium dizonium, n. sp. (Pl. 93, fig. 3).

Tympaniscus dizonius, Haeckel, 1882, Manuscript.

Both rings elliptical, of nearly equal height, smooth, without spines. Sagittal ring with four pairs of small pores (two apical pairs and two basal pairs). Frontal ring with three pairs of small pores (one pair lateral, one pair above and one pair below).

Dimensions.—Height of the frontal ring 0.08, breadth 0.12.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

2. Zygostephanium paradictyum, n. sp. (Pl. 93, fig. 4).

Frontal ring kidney-shaped, in the upper half convex, in the lower concave, in the latter with a deep sagittal constriction. Sagittal ring ovate, about two-thirds as high as the frontal ring. Both rings three-edged, armed with numerous short and branched bristle-shaped spines, which anastomose along their three edges and produce two series of irregular polygonal pores.

Dimensions.—Height of the frontal ring 0.08, breadth 0.13.

Habitat.—North Pacific, Station 236, surface.

3. Zygostephanium constrictum, n. sp.

Frontal ring violin-shaped, concave on the upper and lower margins, with a deep sagittal constriction. Sagittal ring ovate, about two-thirds as high as the frontal ring. Both rings covered with numerous branched irregular spines, which partly anastomose along the edges of the rings, and produce small irregular polygonal pores.

Dimensions.—Height of the frontal ring 0.12, breadth 0.18.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

Definition.— with five large gates (four lateral and one basal). Skeleton composed of three rings, perpendicular one to another, two of which are vertical and incomplete (the primary or lateral, and the secondary or frontal), the third is horizontal and complete (the tertiary or basal ring).

Definition.— with five large simple gates (four lateral and one basal). Skeleton composed of two incomplete meridional rings and one complete basal ring, without lattice-work.