Page:Scientific results HMS Challenger vol 18 part 2.djvu/791

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Definition.— with three articulate feet on the peristome.

The genus Cortinetta comprises Medusettida which exhibit the minimum number of feet, three, and which therefore may be compared to the tripodal (Cortina, Cortiniscus, Tripodiscus, &c.). This similarity is the greater, as in the few observed species an apical horn is developed (as also in the following genus). The three feet are in the two species observed of equal size and similar form, and equidistant, so that they cannot be distinguished as an odd caudal and two paired lateral feet, as in the similar.

1. Cortinetta tripodiscus, n. sp. (Pl. 117, fig. 7).

Shell campanulate, covered with numerous curved ascending bristles, with a prominent annular velum on the peristome, similar to that of Medusetta craspedota. (Pl. 120, fig. 4). Feet equal, widely divergent and equidistant, somewhat longer than the shell, slightly curved, and covered on their convex outer edge with a series of short lateral branches, the three ramules of which bear a spathilla. Apical horn conical, straight, about as long as the shell, also covered with curved bristles.

Dimensions.—Length of the shell 0.14, breadth 0.11; length of the feet 0.16, of the apical horn 0.11.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

2. Cortinetta cortiniscus, n. sp.

Shell campanulate, subspherical, thorny, with a prominent annular velum on the peristome. Feet equal, very large, widely divergent, about three times as long as the shell and studded with arborescent branches, similar to those of Gazelletta drymonema (Pl. 118, fig. 1). Apical horn slender, conical, straight, thorny, twice as long as the shell.

Dimensions.—Length of the shell 0.18, breadth 0.16; length of the feet 0.5 to 0.6, of the apical horn 0.33.

Habitat.—Central Pacific, Station 274, depth 2750 fathoms.

Definition.— with four equidistant articulate feet of equal size on the peristome.

The genus Medusetta comprises those forms of the family which bear on the peristome four equal radial feet, and therefore exhibit a striking similarity to many