The central capsule of the Ellipsida is in all cases ellipsoidal, and occupies the largest part of the shell, being separated from its inner surface by a thinner or thicker jelly-mantle.
Synopsis of the Genera of Ellipsida.
| Ellipsoidal shell without polar appendages (neither solid spines nor hollow tubes at the poles of the axis). | Surface without radial spines. | Shell cavity simple, without an axial rod, | 122. Cenellipsis. | ||
| Shell cavity with a transverse axial rod, | 123. Axellipsis. | ||||
| Surface covered with radial spines, | 124. Ellipsidium. | ||||
| Ellipsoidal shell with polar appendages (either solid spines or hollow fenestrated tubes) at the poles of the main axis. | Solid spines of similar shape, at both poles of the main axis. | Shell cavity simple, without axial rods, | 125. Ellipsoxiphus. | ||
| Shell cavity with a cross of axial rods, | 126. Axoprunum. | ||||
| Solid spines of different shape, at both poles of the main axis. | Two polar spines of different shape, | 127. Ellipsostylus. | |||
| A bunch of spines at one pole only, | 128. Lithomespilus | ||||
| Only a single spine at one one pole, | 129. Lithapium. | ||||
| Two hollow fenestrated tubes opposite, at the poles of the main axis, | 130. Pipettella. | ||||
Genus 122. Cenellipsis,[1] n. gen.
Definition.—Ellipsida with simple ellipsoidal shell, without radial spines and without polar tubes.
The genus Cenellipsis is the simplest and most primitive form, not only among the Ellipsida, but also among the Prunoidea, and it may therefore be regarded as the common ancestral form of the whole family. It corresponds to Cenosphæra among the Sphæroidea, to Cenodiscus among the Discoidea, to Cenolarcus among the Larcoidea. Probably it is derived from Cenosphæra by prolongation of one axis.
Subgenus 1. Cenellipsium, Haeckel.
Definition.—Network of the shell regular, with meshes of equal size and similar form.
- ↑ Cenellipsis = Hollow ellipsoid; κενός, ἔλλειψις.
