1 5 8 



Cincinnati Society of Natural History. 



The original description was as follows : 



"Testa ovata, antice undato angulata, compressa, postice orbicu- 

 lata, transversim sulcata et rugosa ; rugis prope margined obsoletis, 

 serie nodulorum a natibus versus margines, inferiorem decurrente, 

 instructis; natibus decorticatis et leviter erosis ; periostracha nitida, 

 luteofusca; intus alba iridescente ; dentibus crassis, striatis. Plate 3. 



" Hunched Unio. — Shell oval compressed, thin and slightly angu- 

 lar at the anterior end or margin, regularly rounded, convex and thick 

 at the posterior margin, slightly incurved and but little eroded, from 

 the beaks over the disk and near the middle of the shell there is a 

 remarkable gibbosity or nodulous ridge, produced by the striae be- • 

 coming in this place remarkably thick and tuberculated. There 

 appears also in some specimens the indications of a second ridge near 

 the anterior end ; both these ridges are alternately raised and depressed : 

 periostracha much wrinkled by the striae, of a light horn color, and 

 remarkably glabrous, in old and young specimens, it is darker than 

 the perfect shell, and the young are often beautifully rayed and spot- 

 ted with brown ; nacre commonly white, pearly and iridescent : teeth 

 moderately thick, length about two inches, breadth about four. 



"This shell inhabits probably all the western waters; and it is a 

 little remarkable that Prof. Rafinesque, who has described and figured 

 so many of the Unionidae, should have omitted this remarkable 

 species. I found eight or ten of these shells in the river in the neigh- 

 borhood of Pittsburg. In old shells the anterior margin is often pro- 

 duced and truncated, and the young specimens seem to be peculiarly 

 liable to a preternatural enlargement of some portions of the shell 

 more than others." 



Seven years prior to this description Prof. Rafinesque had de- 

 scribed a shell from the Falls of the Ohio River, at Louisville, Ken- 

 tucky, where Unio cesopus is a common form, to which he gave the 

 name Obliguaria cyphyd* and which he has characterized as follows : 



" 29. Espece. Obliquaria cyphya (Unio cyphia.) Obliquaire 

 cyphie. 



"Test epais bombe, bossele, bord flexueux, en talus posterieure- 

 ment; epiderme brun-chatain ; tubercule a rides flexueuses : nacre 

 blanche. Longueur 8-9, diametre et axe 5-9 de la largeur. 



* Vide : Annales Generales des Sciences Physiques, Bruxelles, Septembre 1820. 

 Page 305. 



