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.
Genus 316. Sorolarcus,[[356]] n. gen.
Definition.—Soreumida 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 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.
Subgenus 1. Sorolarcium, Haeckel.
Definition.—Shell without radial spines.
1. Sorolarcus larnacillifer, n. sp. (Pl. [49], fig. 13).