UNIO. 



3. Unio glabratus ? Lam. a shell which agrees with Lamarck's descrip- 

 tion as far as it goes, but he does not mention the fact, that in his shell the an- 

 terior tooth or lamina is almost obsolete, which is the case in ours. 



4. Unio brevialis ? Lam. 



5. Unio alatus. Lam. this is a remarkable species, because it seems to 

 form a link connecting Unio with Hyria; from which, however, it is evidently 

 distinct, as it has only the anterior wing, and its cardinal teeth are not in X\\^ 

 least elongated. 



