PHYSA. 



167 



Subgenus I S I D R A, Ehrenherg. 



46. PHYSA INTEGER, Hold. 



Monog. p. 83, t. 4, f. 7—8. 

 Physa Niagarensis, Lea. — Plate 8, fig. 5. 



I cannot detect the slightest diiFerence 

 between Mr. Lea's species and the previously 

 published integer. It is a very common shell 

 in the Great Lakes and St. Lawrence River, 

 but becomes rarer to the southward, and has 

 not been reported south of Tennessee. 



47. PHYSA DISTORTUS, Haldeman. 

 Monog. p. 35, t. 5, f. 1—3. 



Subgenus A M E R I A, H. Adams. 



(83) 



