480 



Henry Woods — TJie Genus Desorella. 



but as of uncertain position. The simple ambulacra and elongate 

 apical disc clearly separate it from that family. There can, I think, 

 be no doubt that it should be referred to the Echinoneidas, as was 

 done by Desor, De Loriol, and Cotteau. Desorella is also related 

 to Hyboclypeiis, but is distinguished from it by the absence of 

 a dorsal sulcus. 



Desorella elata (Desor). (Plate XVI.) 



Synonymy. 



1847. 



raisonne des 



Hijhoclypus elatus, Desor : in Agassiz & Desor, " Catal. 



E'chinides," Aun. Sci. nat., ser. iii, vol. vii, p. 152. 

 1855. Desoria elata, Cotteau: E'chin. Foss. de I'Yonne, vol. i, p. 228, pi. xxxiv, 



figs. 1-3 {Desorella on p. 344). 

 1855. Desorella elata, Cotteau: Bull. Soc. geol. France, ser. ii, vol. xii, p. 713. 

 1857. Desorella elata, Desor: Synopsis E'chin. Foss., p. 194. 

 1873. Desorella elata, GotteaM: Pal. Frau^. Terr. Jur., vol. ix, p. 386, pis. xcviii, 



xcix, figs. 1,2. 



Description. — Test large, subcircular, subrostrate and slightly 

 truncate posteriorly, flattened, aboral surface regularly convex, 

 mai'gins rounded. Apex slightly posterior to the centre. Base 

 concave, distinctly undulating ; peristome sub-pentagonal, oblique, 

 placed a little in front of the centre. Periproct large, ovate, at the 

 posterior end and extending to the margin of the aboral surface ; 

 dorsal. sulcus absent, the test depressed around the lower part of 

 the periproct. 



Fig. 1. — Apical disc of specimen shown in Plate XVI. x 3. 



Apical disc elongate, slightly depressed, all the plates bearing 

 small granules. Anterior ocular indistinctly shown. Madreporic 

 plate large, in contact with the left anterior genital, which is divided 

 into two parts. Eight antero-lateral ocular smaller than the left, 

 and separated from it by a large, nearly hexagonal, complementary 

 plate which touches, in front, the madreporic plate and the left 

 anterior genital plate. Postero-lateral genitals large, separated 



