Plate XXI. 



Urechinus Naresianus Al. Ag. 



p. 9U. 



Fi?. 239. The skeleton of Urecliimts Naresi;\iuis Ai,. Ac, laid out. 



Fi^. 210. The buccal membrane of the same. 



Fi?. 241. The anal membrane of the same. 



Fio-. 242. The calvcinal system of tlie same. 



