OF THE UNITED STATES. 177 



by the much more rapid attenuation of the spire, and 

 in the proportional difference in the length of the 

 aperture, which in the virginica is not more than 

 equal to the length of the second and third whirls. 



4. M. *prcerosa. Shell subglobular, oval, horn 

 colour; volutions three or four, wrinkled across; 

 spire very short, much eroded, in the old shell, so 

 much so as to be sometimes not prominent above the 

 body whirl, body whirl large, ventricose, with a very 

 obtuse, slightly impressed revolving band ; aperture 

 suboval, above acute and effuse 5 within on the side 

 of the exterior lip about four revolving purplish lines, 

 sometimes dotted, sometimes obsolete or wanting; 

 labium thickened, particularly at the superior termi- 

 nation near the angle, and tinged with purplish 5 

 base of the columella somewhat elongated and in- 

 curved, meeting the exterior lip at an angle. 



Length about 4-5 inch. 



Inhabits Ohio River. 



Found in plenty at the falls of the Ohio, the spire 

 is remarkably carious in the older shells, and the 

 penultimate whirl, between the aperture and the 

 spire is also remarkably eroded in many older shells. 

 The spire in the young shell is entire, and but little 

 prominent though acute, and the bands are distinct on 

 the exterior of the shell. This shell does not seem 

 to correspond with the genus to which I have for the 

 present referred it, and owing to the configuration of 

 the base of the columella, if it is not a Melanopsis, 



83 



