Page:Scientific results HMS Challenger vol 18 part 2.djvu/806

1682 2. Castanarium hookeri, n. sp.

Pores regular, circular, hexagonally framed, twice as broad as the bars. Radial bristles one-third as long as the radius.

Dimensions.—Diameter of the shell 0.55, of the pores 0.025.

Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.

3. Castanarium lyelli, n. sp.

Pores regular, circular, without hexagonal frames, of the same breadth as the bars. Radial bristles twice as long as the diameter of one pore.

Dimensions.—Diameter of the shell 0.24, of the pores 0.015.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

4. Castanarium lubbocki, n. sp.

Pores irregularly roundish, about of the same breadth as the roundish, non-crested bars. Radial bristles one-third as long as the radius.

Dimensions.—Diameter of the shell 0.36, of the pores 0.01 to 0.02.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

5. Castanarium huxleyi, n. sp.

Pores irregularly polygonal, two to three times as broad as the bars, separated by prominent polygonal crests. Radial bristles half as long as the radius.

Dimensions.—Diameter of the shell 0.45, of the pores 0.02 to 0.05.

Habitat.—South Pacific (off Australia), Station 165, surface.

Definition.— without radial main-spines, with a dentate mouth.

The genus Castanella comprises the most common and most widely distributed species of Castanellida. It agrees in general shape with its ancestral form, the preceding Castanarium, differing from it only in the possession of strong teeth, which form a corona around the mouth.