Page:Scientific results HMS Challenger vol 18 part 2.djvu/793

Rh 5. Medusetta tetranema, n. sp. (Pl. 120, fig. 3).

Shell campanulate, conical, smooth, nearly twice as broad as the constricted mouth, without prominent velum. Apical horn somewhat shorter, straight, conical, thorny. Feet strongly curved inwards, convergent, twice as long as the shell, each with four to six strong, ascending, alveolate branches on the abaxial margin.

Dimensions.—Length of the shell 0.07 to 0.09, breadth 0.05 to 0.07.

Habitat.—Tropical Atlantic, Station 352, surface.

6. Medusetta spiralis, n. sp.

Shell hemispherical, thorny, with wide open mouth. Apical horn straight, vertical, thorny, twice as long as the shell; feet cylindrical, three times as long as the shell, spirally convoluted around the vertical axis of the shell, with a series of recurved teeth on the abaxial margin.

Dimensions.—Length of the shell 0.05, breadth 0.08.

Habitat.—Central Pacific, Stations 271 to 272, surface.

7. Medusetta craspedota, n. sp. (Pl. 120, fig. 4).

Shell campanulate or nearly spherical, spiny, twice as broad as the constricted mouth, which is surrounded by a funnel-shaped truncate velum. Apical horn conical, straight, spiny, half as long as the shell. Feet strongly curved, longer than the shell, with a series of short conical spines on the abaxial side.

Dimensions.—Length of the shell 0.06, breadth 0.06.

Habitat.—North Pacific, Station 239, surface.

Definition.— with four articulate feet on the peristome, one odd very large, and three small or rudimentary feet.

The genus Euphysetta agrees with the preceding Medusetta in the possession of four articulate feet; but whilst these in the latter are of equal size and similar shape, in the former a single odd foot only is developed, and very large, whilst the three others are rudimentary and very small. Euphysetta exhibits therefore the same relation to Medusetta that the Euphysidæ (Euphysa, Steenstrupia, &c.) bear to the Sarsiadæ (Codonium, Sarsia), among the Hydromedusæ (compare my System der Medusen, 1879, vol. i. p. 12).