Cortical shell thin walled, with thorny surface; pores irregular, roundish, of very unequal size, twice to six times as broad as the bars; twelve to eighteen on the half meridian, eight to thirteen on the half equator. Between the pores irregularly scattered, bristle-like, thin spines about the same size, partly straight, partly oblique, rising from the surface. Medullary shell lenticular, compressed, its equatorial axis one and a half times the length of the main axis, and about half that of the cortical shell.
Dimensions.—Main axis of the cortical shell 0.15, equatorial axis 0.09; meshes 0.004 to 0.02, bars 0.003 to 0.006; length of the spines 0.02; diameter of the medullary shell 0.04.
Habitat.—South Atlantic, Station 318, surface.
Genus 156. Cyphonium,[[195]] n. gen.
Definition.—Cyphinida with simple cortical shell and double medullary shell, without polar spines or tubes.
The genus Cyphonium contains a number of very common species, among which are the earliest known forms of this family, partly described by Ehrenberg as Ommatospyris (which genus contains also a number of other Prunoidea), partly by me (1862) as Didymocyrtis. Both names are inadequate, as allusions to quite different families of Nassellaria, but may be retained as significations of subgeneric divisions. Cyphonium differs from Cyphanta by the double medullary shell, which is either spherical or lenticular.
Subgenus 1. Ommatospyris, Ehrenberg (partim).
Definition.—Surface of the cortical shell smooth, without thorns or spines.
1. Cyphonium coscinoides, n. sp.
Ommatospyris coscinoides, Haeckel, 1881, Prodromus, p. 462.