Page:Scientific results HMS Challenger vol 18 part 1.djvu/923

Rh shell exhibits quite the same characteristic structure as that of Larnacilla, being composed of three elliptical latticed girdles, perpendicular one to another. In some species also the beginning of a second system of girdles is clearly indicated, so that there can be no doubt as to their derivation from Amphipyle or Tetrapyle.

Definition.—Shell without radial spines.

1. Sorolarcus larnacillifer, n. sp. (Pl. 49, fig. 13).

Shell irregular, clustered, or tuberous, composed of twenty to thirty irregular, roundish chambers of very different size, the largest four to eight times as broad as the smallest, aggregated without order around a central, lentelliptical, Larnacilla-shaped medullary shell. Pores irregular, roundish, twice to four times as broad as the bars. Surface smooth or a little spiny.

Dimensions.—Diameter of the whole shell 0.18, of the central Larnacilla-shell 0.05.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

2. Sorolarcus tetrapylifer, n. sp.

Shell irregularly roundish, clustered, composed of ten to twelve irregular rather long chambers of almost uniform size, the largest twice as broad as the smallest, aggregated without order around a central shell of the structure of Tetrapyle, which encloses an inner trizonal Larnacilla-shell of half the size. Pores irregular, roundish, twice to four times as broad as the bars. Surface spiny.

Dimensions.—Diameter of the whole shell 0.25, of the outer (Tetrapyle-like) medullary shell 0.12, of the inner (Larnacilla-like) shell 0.06.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

Definition.—Shell with radial spines.

3. Sorolarcus terminalis, n. sp.

Shell nearly spherical, composed of fifteen to eighteen irregularly aggregated roundish chambers of nearly equal size; in the centre a lentelliptical Larnacilla-shell. Surface covered with numerous thin, bristle-like radial spines, somewhat longer than the shell.

Dimensions.—Diameter of the whole shell 0.21, of the central Larnacilla-shell 0.05.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.