Dimensions.—Diameter of the disk 0.1, pores 0.005; length of the spines 1 to 1.2 or more, breadth 0.01.
Habitat.—Indian Ocean, Ceylon, surface, Haeckel.
Genus 179. Crucidiscus,[[218]] n. gen.
Definition.—Cenodiscida with four radial spines on the margin of the disk, crossed in the equatorial plane.
The genus Crucidiscus is the most simple form of the Staurodiscida, or of the numerous Discoidea (belonging to different families) in which the margin of the disk bears four radial spines, lying in the equatorial plane, and crossed at right angles. Whilst commonly the internal shell-cavity of Crucidiscus is quite simple, in one case it bears four centripetal axial rods, as inner prolongations of the outer radial cross-spines, perhaps indications of a lost medullary shell (comp. p. [410]).
Subgenus 1. Staurentodiscus, Haeckel.
Definition.—Internal cavity of the shell with centripetal axial rods.
1. Crucidiscus endostaurus, n. sp. (Pl. [48], fig. 2).
Disk with smooth surface and smooth simple margin. Pores regular, circular; thirteen to fourteen on the radius of the disk. Four crossed spines conical, strong, longer than the radius of the disk, on the inside prolonged into four thinner centripetal axial rods, which do not reach the centre. In the middle part of the disk also some other short axial rods arise from the inside, not reaching the centre (as in Stylodiscus endostylus, Pl. [31], fig. 11).
Dimensions.—Diameter of the disk 0.16, of the pores 0.004; length of the spines 0.2, breadth 0.014.