PHYSA MICROSTOMA. 39 



cupying considerably more than half the entire 



area of the shell; fold well marked: whirls three. 



Foreign Analogue. Amphipeplea involuta. 



OBSERVATIONS. 



This small species inhabits the submerged 

 rocks, in the rapids at the mouth of Nolachucky 

 river, in Tennessee, under such circumstances 

 as to convince me that it does not breathe the 

 free air. I procured but two individuals, the 

 shells of which are sufficiently translucent to 

 exhibit light circular dots upon the black ground 

 of the mantle; a common character in this 

 genus. 



PHYSA MICROSTOMA, Hald. 



Plate 4.— Figs. 12—14. 



P. testa crassa, laevi, pallida, elliptica; anfractibus 4 

 planiusculis: labio crasso; columella bidentata. 



SYNONYMS AND REFERENCES. 



Physa (Physodon) microstoma. This work, October 

 1840. 



