Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface from many Stations.
2. Rhizosphæra serrata, n. sp. (Pl. [18], figs. 5-7).
Central cavity of the spongy shell five times as broad as the diameter of the outer medullary shell. Bars of all three shells of the same breadth as the forty to sixty (or more) thin radial beams between them. These are three-sided prismatic, with denticulate edges, scarcely half as broad as their outer prolongations, which are half as long as the shell radius, and possess three spirally contorted serrated edges. (The figured specimen is a young one; in the older specimens the spongy framework of the cortical shell is much more developed.)
Dimensions.—Diameter of the spongy shell 0.3, of its central cavity 0.22, outer medullary shell 0.06, inner 0.02.
Habitat.—Central Pacific, Stations 270 to 274, surface.
3. Rhizosphæra leptomita, Haeckel.
Rhizosphæra leptomita, Haeckel, 1862, Monogr. d. Radiol., p. 453, Taf. xxv. figs. 8-10.
Central cavity of the spongy cortical shell twice as broad as the diameter of the outer medullary shell; bars of both very thin, only one-third as broad as the bars of the inner medullary shell. Radial spines thirty to fifty (or more), curved, three-sided prismatic; inside the spongy shell as thin as their bars, outside three times as broad.
Dimensions.—Diameter of the spongy shell 0.27, of its inner cavity 0.2, outer medullary shell 0.1, inner 0.05.
Habitat.—Mediterranean (Messina); Atlantic, Stations 348 to 354, surface.