

No. IV. 



Description of Six New Species of the Genus Unio, embrac- 

 ing the Anatomy of the Oviduct of one of them, togethe)- 

 with some Anatomical Observations on the Genus. By 

 Isaac Lea. — Read before the American Philosophical Society 

 November 2d 1827. 



WN the present contribution to the science of Conchology, I 

 *have endeavoured to be as brief as I thought the subject 

 would permit. 



I have often felt the great inconvenience sustained from 

 too short and indefinite descriptions; and am therefore fully 

 sensible of the necessity, for the proper distinction of the spe- 

 cies, of a more minute notice of their characters than is usu- 

 ally given. In this Mr Barnes has shewn a laudable example, 

 and he deserves the acknowledgments of the conchologist*. 



It will be observed I have followed his plan of dividing the 

 margin of the disk into eight parts, reversing his posterior and 

 anterior margins. 



• Swainson says, " Although Lamarck has described so many (Uniones), the 

 short descriptions he has given, and the want of figures to elucidate them, render it 

 impossible to determine accurately one half the species which he has enumerated " 



Division of i^^ilusks 

 Sactianal Library 



