JVew species of Fresh Water Shells. 343 



Inhabits Alabama river, adhering to pebbles on the bars. Cabinet 

 of the Academy of Natural Sciences of Philadelphia. 



Unio subtentus. Say. var. PI. 1. fig. 3. 



This beautiful variety of the U. subtentus was found by rae in the 

 Tennessee and Elk rivers. The annexed delineation of the species 

 is probably better than any hitherto given. 



Unio mttilloides. Raf. var. PI. 1, fig. 7. 



I obtained this shell in the Alabama river. Its characters appear 

 to be intermediate between U. ellipsis, Lea, and U. mytilloides, 

 Raf., yet is doubtless identical with the latter species. 



SUPPLEMENT. 



Planorbis antrosus. 



Shell dextral, not depressed ; whorls three ; spire profoundly in- 

 dented, or concave, with the summit of the body whorl angular ; in- 

 ner volutions angulated ; umbilicus profound, with the margin and 

 inner volutions angulated : body whorl abruptly dilated near the 

 aperture ; aperture longitudinally subovate, dilated. 



Melania congesta. 



Shell subulate, with about nine volutions, the lower ones obscurely 

 angulated, those of the spire becoming acutely carinated towards the 

 apex; suture well defined; body whorl obscurely sub-angulated ; 

 aperture longitudinal, elliptical. 



Physa pomilia. 



Shell with four volutions, horn colored and polished ; spire short 

 conical; body whorl ventricose ; aperture patulous. — Remark. It 

 resembles P. heterostropha, Say, but is much smaller and thinner. 



These three univalves inhabit Randon's creek, near Claiborne, 

 Alabama, adhering to Limestone rocks. 



(To be contimicd.) 



