OF THE UNITED STATES. 175 



4. P. Hustrica. Shell conic; whirls slightly 

 wrinkled, convex: suture profoundly indented ; aper- 

 ture oval nearly orbicular ; labrum with the superior 

 edge not appressed to the preceding whirl, but sin> 

 ply touching it ; umbilicus rather large, rounded. 



Length less than i-10 of an inch. 



Cabinet of the Academy. 



The smallest species I have seen. The aperture 

 somewhat resembles that of a Valvata, to which ge- 

 nus it may probably be referrible. Mr. Jessup ob- 

 tained two specimens, on the shore of Cayuga Lake. 



Genus Melania. 



1. M. *canaliculata. Shell tapering, horn-colour ; 

 volutions about seven, slightly wrinkled ; spire to- 

 wards the apex much eroded, whitish ; body with a 

 large obtuse groove, which is obsolete upon the 

 whirls of the spire, in consequence of the revolution 

 of the suture on its inferior margin ; this arrange- 

 ment permits the superior margin of the groove, only, 

 to be seen on the spire, in the form of an obtuse ca- 

 rina on each of the volutions ; aperture bluish- white 

 within, with one or two obsolete revolving sangui- 

 neous lines; labrum slightly undulated by the 

 groove, and with a distinct sinus at the base of the, 

 columella. 



Inhabits Ohio River. 



Length one inch and one tenth. 



Breadth 3-5 of an inch. 



Greatest transverse diameter more than 2-fc 



