Page:Scientific results HMS Challenger vol 18 part 2.djvu/90

966 four feet simple, curved, with three edges, the posterior (caudal) foot larger, the anterior (sternal) foot smaller than the two lateral (pectoral) feet.

Dimensions.—Height of the sagittal ring 0.09, breadth 0.07.

Habitat.—Tropical Atlantic, Station 351, surface.

4. Stephaniscus medusinus, n. sp.

Sagittal ring elliptical, thorny, with a larger apical horn. Basal ring nearly square, with short marginal thorns and four large ovate gates of nearly equal size. All four feet of equal size divergent, curved, irregularly branched, with short curved branches.

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

Habitat.—South Atlantic, Station 332, depth 2200 fathoms. Fossil in Barbados.

Definition.— with six typical basal feet (two sagittal, two pectoral, and two tergal feet).

The genus Semantiscus may be the archetype of those which exhibit six typical basal feet, in combination with the sagittal ring. Three of these are the primary feet of Cortina and Cortiniscus, the other three are secondary productions between the former. The basal ring may possess either two, four, or six basal pores.

1. Semantiscus hexapodius, n. sp. (Pl. 92, fig. 16).

Sagittal ring elliptical, with a large branched apical horn. Basal ring small, square, with two small triangular gates (or jugular pores). From its periphery there arise six short and stout cylindrical feet, one very large (caudal) from the posterior corner, two tergal on each side, two opposite (pectoral) from the lateral corners, and one odd sternal from the anterior corner. All six spines bear a bunch of ten to twenty stout pointed conical branches, partly simple, partly forked.

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

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

2. Semantiscus hexaspyris, n. sp. (Pl. 92, fig. 18).

Sagittal ring semicircular, broad, latticed, with two pairs of irregular dorsal and two pairs of ventral pores. The dorsal rod is straight and vertical, prolonged upwards into a short serrate apical horn, downwards into a straight linear caudal foot. The ventral rod is curved and prolonged into a similar sternal foot. Basal ring hexagonal, with four ovate gates (two smaller jugular and two larger cardinal pores); its four lateral corners prolonged into four curved thorny lateral feet (two