Page:Scientific results HMS Challenger vol 18 part 1.djvu/536

328 11. Druppatractus pisciculus, n. sp.

Cortical shell thick walled, spiny, with irregular network. Proportion of the two axes = 3 : 2. Pores irregular, roundish, lobed, or composed of three to five confluent porules, twice to six times as broad as the bars; six to eight on the half equator. (Similar to Ellipsoxiphus atractus, Pl. 14, fig. 1.) Medullary shell ellipsoidal, nearly half as large as the cortical shell. Polar spines three-sided pyramidal, the major longer than the main axis, the minor scarcely one-third to one-fourth as long.

Dimensions.—Major axis 0.18, minor 0.12; pores 0.01 to 0.03, bars 0.004; axes of the medullary shell 0.08 and 0.05; length of the major polar spine 0.2, of the minor 0.05, basal breadth 0.02.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

Definition.— with simple ellipsoidal cortical shell and double medullary shell, in the main axis with two large opposite polar spines of equal size and similar form.

The genus Stylatractus differs from Lithatractus in the double medullary shell, from Amphisphæra in the ellipsoidal form of the cortical shell. As in these two genera, both opposite polar spines have the same shape and size.

Definition.—Network of the cortical shell regular or subregular, with meshes of nearly equal size and similar form; surface smooth, without thorns or papillæ.

1. Stylatractus neptunus, n. sp. (Pl. 17, fig. 6).

Amphistylus neptunus, Haeckel, 1878, Atlas, pl. xvii. fig. 6.

Cortical shell thick walled, smooth, with subregular, circular, polygonally framed pores, quite as broad as the bars; ten to twelve on the half equator. Polar spines three-sided pyramidal, about as long as the half main axis, three times as broad at the base as the pores. (Much resembles Amphisphæra neptunus, p. 142, but differs from it by the prolongation of the main axis, which equals one and a half or one and a fourth the equatorial axis, and by the somewhat irregular formation of the cortical hexagonal network. Sometimes also, as in the figured specimen, the length of both polar spines is somewhat different.)

Dimensions.—Major axis of the cortical shell 0.15, minor axis 0.12; pores and bars 0.007; main axes of both ellipsoidal medullary shells 0.08 and 0.05; length of the polar spines 0.08 to 0.1, basal breadth 0.02.

Habitat.—Pacific, central area, Stations 266 to 268, depth 2700 to 2900 fathoms.