Page:Scientific results HMS Challenger vol 18 part 2.djvu/589

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Definition.— (vel Stichocyrtida multiradiata clausa) with nine radial ribs or wings.

The genus Stichophæna differs from the preceding Artophæna in the typical number of the radial lateral appendages, being nine in the former, six in the latter. Usually these are simple ribs enclosed in the shell-wall, more rarely prominent wings.

Definition.—Last joint of the shell rounded, without basal spines.

1. Stichophæna ritteriana, n. sp. (Pl. 75, fig. 12).

Shell pear-shaped, twice as long as broad, with seven internal annular septa. The upper half is slenderly conical, composed of seven joints of nearly equal length, gradually increasing in breadth. The lower half is formed only by the eighth joint, which is very large, subglobose, inflated, and as long as the seven other joints together. The spherical cephalis bears a conical horn of the same length. From the thorax arise at equal distances nine radial ribs in the form of thin, triangular lamellæ, which attain their greatest height in the sixth joint, and form nine elegant, denticulate crests in the eighth joint. Pores small and numerous, subregular, circular. This beautiful species is dedicated to my honourable friend, Dr. Paul von Ritter, the magnanimous philanthropist and liberal protector of free science, who founded in the University of Jena the first professorial chair of Darwinism and phylogeny.

Dimensions.—Length of the shell (with eight joints) 0.24, breadth 0.12. Length of each of the first seven joints 0.015; diameter of the subspherical last joint 0.12.

Habitat.—South Pacific, Station 300 (off Juan Fernandez), depth 1375 fathoms.

2. Stichophæna darwiniana, n. sp.

Shell pear-shaped, twice as long as broad, with six distinct strictures. The last joint is the broadest and twice as long as the sixth, three times as long as each of the five preceding joints. The hemispherical cephalis bears a conical horn of twice the length. From the third joint arise nine radial ribs, which reach the sixth joint, but are not developed in the last hemispherical joint. Pores irregular, roundish.

Dimensions.—Length of the shell (with seven joints) 0.2, breadth 0.1. Length of five first joints, each 0.018 to 0.022, of the sixth 0.03, of the seventh joint 0.06.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.