PLANORBIS. 203 



17. PLANORBIS BICARINATUS, Say. 



Hald. MoDog. p. 6, t. 1, figs. 1 — 6. 



Distributed throughout the entire country 

 east of the Rocky Mountains, but commonest 

 in the waters of the Eastern and Middle 

 States. 



Planorhis lautns, H. Adams, from New Or^ 

 leans, has never been figured, nor have I seen 

 an authentic specimen, but, judging from the 

 description, I think it probable that it is the 

 young of this species. 



Planorhis antrosus, Conrad, I am also 

 inclined to place in the synon3niiy of hicarinor 

 tus. It has not been figured, and, if different, 

 has not been included in any of the numerous 

 collections sent to us by zealous explorers like 

 Dr. E. R. Showalter, who have so thoroughly 

 examined the waters of Alabama for Mol- 

 lusca. Mr. Conrad himself has no recollection 

 of his species, which he described over thirty 

 years ago. 



(50) 



