146 CIDARITES. 



ECHINID.E. CIDARITES. 



Genus Cidaris. Leske. 



Generic Character. — Body globose ; anus and mouth nearly equal. Ambulacra 

 continuous from mouth to anus, which are both central, the former below, the 

 latter above ; spiniferous tubercles perforate ; spines of several forms. 



THE PIPER. 

 Cidaris papillata. Leske. Fleming. 



Specific Character. — One tubercle on each inter-ambulacral plate, none on the 

 ambulacra] ; spines long, cylindrical, regularly ridged with distant crenated ridges. 



Cidaris papillata, Fleming, Brit. An. p. 477. Encyc. Meth. t. exxxvi. 



f. C, 7. 

 Echinus Cidaris 1 var. a. Sowerby, Brit. Misc. tab. xliv. 



This, the most elegant of all our native Sea-Urchins, is 

 by far the rarest, being confined to the Zetland seas. It 

 measures about one inch and three quarters across, and is 

 of a depressed globose form. The anal opening of the shell 

 is as wide as the oral, and the latter is furnished internally 

 with five erect plates, which are divided in the centre 

 nearly to their bases, so as to give the appearance of ten 

 plates. These serve for the attachment of the muscles of 



