Page:Scientific results HMS Challenger vol 18 part 2.djvu/800

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Definition.— with numerous (ten to twenty or more) articulate feet.

The genus Polypetta comprises those Medusettida in which the number of feet is very large and not limited, usually twenty to thirty or more. The few specimens of this genus that have been observed are rather different; and it may be that only the two first species described in the following lines are true Medusettida; they possess the usual distinctly alveolate feet, and are derived from the similar Medusetta or Gazelletta simply by multiplication of the feet. The two other species, however (figured in Pl. 116, figs. 1, 2, as Porospathis), belong perhaps to another family of (Castanellida?); their shell-structure is peculiar and their feet not distinctly alveolate; they may therefore represent a peculiar genus Porospathis (Haeckel, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, 1879, p. 5).

1. Polypetta polynema, n. sp.

Shell campanulate, thorny, about as long as broad, with slightly constricted mouth, similar to that of Gazelletta orthonema (Pl. 120, fig. 10). Shell-wall hollow, with irregular polygonal alveoles. Peristome with a corona of eighteen divergent, curved, cylindrical feet of unequal size; six larger primary on the margin of the shell, the other twelve secondary, between the former, somewhat above the margins at different heights. The feet are two to three times as long as the shell, irregularly curved and distinctly alveolate, without appendages.

Dimensions.—Length of the shell 0.12, breadth 0.11.

Habitat.—Central Pacific, Station 266, surface.

2. Polypetta alveolata, n. sp.

Shell campanulate, thorny, about as long as broad, very similar to that of Medusetta craspedota (Pl. 120, fig. 4). Shell-wall hollow, with subregular hexagonal alveoles. Peristome prolonged into a short funnel-shaped proboscis, twice as long as the similar velum of the latter. The velum is surrounded by a corona of eight larger and eight to twelve smaller feet; the larger are about as long as the shell, divergent, irregularly curved, thorny, and distinctly alveolate; the smaller feet are scattered above the latter and form an immediate transition to the small spines of the shell-surface.

Dimensions.—Length of the shell 0.08, breadth 0.09.

Habitat.—South Pacific, Station 284, surface.