Habitat.—South Atlantic (east coast of Patagonia), Station 318, surface.
Subfamily 3. Cenocapsida, Haeckel.
Definition.—Radial spines completely reduced and absent; shell cavity therefore simple; shell pierced by twenty perspinal pores (each placed in the direction of one radial spine which has disappeared).
Genus 348. Cenocapsa,[[388]] n. gen.
Definition.—Sphærocapsida without radial spines, with simple cavity of the spherical shell, which is pierced by twenty perspinal holes (each one placed in the radial direction of one spine which has disappeared).
The genus Cenocapsa comprises only a single species, but is very remarkable in that it is the most reduced form among all Sphærocapsida. The twenty radial spines of the Icosacantha have perfectly disappeared by complete retrograde metamorphosis, and the only evidence of their former existence (in the ancestral genus Porocapsa) are the twenty perspinal holes remaining in the shell. Cenocapsa is the only form of Acantharia which possesses no radial spines.
1. Cenocapsa nirvana, n. sp. ([133], fig. 11, 11a, 11c).
Perspinal holes four-lobed, cruciform, with four short triangular teeth between the four lobes of the cross. Poruli of the shell in the bottom of an elliptical dimple surrounded by an elevated ring.
Dimensions.—Diameter of the shell 0.2 to 0.3, of the aspinal holes 0.02.
Habitat.—North Pacific, Station 248, surface.