Page:Scientific results HMS Challenger vol 18 part 1.djvu/594

386 bristle-like spines. On both poles of the main axis a bunch of six to eight aggregated larger conical spines, about as high as a single chamber.

Dimensions.—Main axis (without polar spines) 0.2, equatorial axis 0.06; pores 0.005 to 0.015, bars 0.003; length of the polar spines 0.05, basal thickness 0.005.

Habitat.—Pacific, central area, Stations 270 to 274, depth 2350 to 2925 fathoms.

4. Panicium coronatum, n. sp. (Pl. 40, fig. 4).

Both proximal chambers kidney-shaped, covered with short stout spines. Pores irregular, roundish, twice to four times as broad as the bars; seven to eight on the half meridian, eleven to thirteen on the half equator of each chamber. Both distal chambers cap-like, separated from the former by a circle of ten to twelve very large square pores; the other pores very small, roundish. The circumpolar area is smooth, surrounded by a circle of ten to twelve very stout, conical, radial spines, which arise from the distal ends of the bars separating the large square meshes.

Dimensions.—Main axis (without spines) 0.22, equatorial axis 0.08; greatest breadth in the equator of the chambers 0.1; pores of the proximal chambers 0.007 to 0.015, bars 0.004; square pores of the distal chambers 0.02 to 0.03, small pores 0.005, bars 0.004; length of the radial spines of the polar circles 0.07, basal thickness 0.007.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

Definition.— with double cortical shell and double medullary shell, on both poles of the main axis with two opposite apical spines, or with a bunch or circle of polar spines.

The genus Peripanicium differs from Panicium only in the development of an outer reticulated envelope, which mantle-like surrounds the shell, and represents a second or external cortical shell. As in Panicium, its ancestral form, so also in Peripanicium, there can be distinguished two subgenera:—Peripanicea, where only a single large spine arises from each pole (lying in the main axis), and Peripanicula, where a variable number of spines is to be found, either diverging bunch-like from the pole itself, or surrounding it as a crown-like polar circle.

Definition.—On both poles of the main axis only a single large spine.

1. Peripanicium amphixiphus, n. sp.

Internal cortical shell with four unequal chambers, with thorny surface. Both proximal chambers kidney-shaped (with subregular hexagonal pores, three times as broad as the bars).