Page:Scientific results HMS Challenger vol 18 part 1.djvu/922

714 4. Soreuma acervulina, n. sp.

Shell quite irregular, cloddy, or tuberous, composed of twenty to thirty (or more) roundish chambers of almost uniform size, the largest twice to three times as broad as the smallest. Pores irregular, roundish. Surface smooth.

Dimensions.—Diameter of the shell 0.18 to 0.24, of the largest chambers 0.06, of the smallest 0.02.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

Definition.—Shell with radial spines.

5. Soreuma spinosum, n. sp.

Shell quite irregular, cloddy, or tuberous, composed of thirty to forty subspherical chambers of nearly the same size. Pores subregular, circular, twice as broad as the bars; on the equator of each chamber six to eight pores. Surface thorny, covered with irregularly scattered conical radial spines, about as long as the diameter of the chambers.

Dimensions.—Diameter of the shell 0.17 to 0.25, of the chambers 0.04.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

6. Soreuma setosum, n. sp.

Shell nearly spherical, composed of sixty to seventy (or more) irregular, roundish chambers of very different sizes, the largest five to six times as broad as the smallest. Pores irregular, roundish. Surface bristly, covered with very numerous, long and thin, bristle-shaped radial spines, about as long as the diameter of the shell.

Dimensions.—Diameter of the shell 0.28, of the chambers 0.005 to 0.03.

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

Definition.— with numerous chambers, aggregated irregularly around a trizonal medullary shell or Larnacilla-shell.

The genus Sorolarcus comprises those Soreumida in which the heap of irregularly aggregated chambers encloses a central trizonal medullary shell, by which they demonstrate clearly their descent from Larnacida or Pylonida. The lentelliptical medullary