290 



THE VOYAGE OF H.M.S. CHALLENGER. 



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. 



Ellipsoidal shell without 

 polar appendages (neither 

 solid spines nor hollow 

 tubes at the poles of the 

 axis). 



Synopsis of the Genera of Ellipsida. 



Shell cavity simple, without 



Surface without radial 

 spines. 



an axial rod, 



Shell cavity with a trans- 

 verse axial rod, . 



Ellipsoidal shell with polar 

 appendages (either solid 

 spines -or hollow fenes- 

 trated tubes) at the poles 

 of the main axis. 



Surface covered with radial spines, 



f Shell cavity uimple, without 

 Solid spines of similar | axial rods, 

 shape, at both poles of -{ 

 the main axis. | Shell cavity with a cross of 



[ axial rods, 



Solid spines of different 

 shape, at both poles of 

 the main axis. 



Two polar spines of 

 different shape, . 



A bunch of spines at one 

 pole only, 



Only a single spine at 

 one pole, 



Two hollow fenestrated tubes opposite, at the poles of the 

 main axis, ...... 



122. CenelUpsis. 



123. Axellipsis. 



124. Elli}ifi<liu)n. 



125. Ellipsoxiphus. 



126. Axoprunum. 



127. Ell/psostylus. 



128. Li th omespilus. 



129. LitJiapium. 



130. Plpdtella. 



Genus 122. CenelUpsis, 1 n. gen. 



Definition. E llipsida with simple ellipsoidal shell, without radial spines and 

 without polar tubes. 



The genus CenelUpsis is the simplest and most primitive form, not only amono- 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 Cenosphcera among 

 the Sphseroidea, to Cenodiscus among the Discoidea, to Cenolarcus among 

 the Larcoidea. Probably it is derived from Cenosphcera by prolongation of 



one axis. 



Subgenus 1. Cenellipsium, Haeckel. 

 Definition. Network of the shell regular, with meshes of equal size and similar form. 



1 Cenellvp$is= Hollow ellipsoid ; xtvo 



