2. Spongechinus serrulatus, n. sp.
Spongy sphere twice as broad as its inner cavity, with a delicate, equal framework. Entire surface covered with short, curved, radial spines, which are elegantly denticulated, and as long as the shell radius.
Dimensions.—Diameter of the sphere 0.3, of its cavity 0.15; length of the spines 0.15.
Habitat.—Central Pacific, Station 274, surface.
3. Spongechinus cavus, n. sp.
Spongy sphere only one-fourth broader than the large inner cavity, its spongy wall being only one-fourth as thick as the radius, composed of three to four strata of irregular, small meshes. Surface covered with short, bristle-shaped, curved spines, one-third as long as the radius.
Dimensions.—Diameter of the sphere 0.5, of its inner cavity 0.4; length of the spines 0.08.
Habitat.—North Atlantic, Station 354, surface.
Genus 114. Spongothamnus,[[153]] n. gen.
Definition.—Astrosphærida with hollow, spongy sphere, without latticed medullary shell in the central cavity, and with numerous branched radial spines.