[71 ] 



POMATIA, Leach. 

 1. Pomatia aspersa, Muller. 



Plate 6, figure 16. 



Subglobose, rather thin, coarsely and irregularly striate, 

 finely striate and finely wrinkled and indented ; spire obtuse ; 

 whorls 4-5, moderately convex, rapidly increasing, the last 

 very large and ventricose; aperture large, oblique, rounded- 

 lunate, lip white, sharp, a little expanded, extremities con- 

 nected by a thin callus ; umbilicus covered ; base very con- 

 vex. Yellowish or brownish, with brown bands, crossed by 

 narrow undulating flammules of yellow. 



Diam. 31, height 25 mill. 



At various places on the Coast, New Orleans, Charleston. 

 Maine, Nova Scotia. (From Europe.) 



MESODONTIN^. 



Genera. 



* Shell minute, margin of lip circular, its extremities 

 approaching and connected hy a callus : not toothed. 



1. Vallonia, Risso. Shell minute, diaphanous, umbilicate ; 



lip margin broadly reflected, nearly circular, white. 



European ; extending into the States east of the Rocky 

 Mountains. 



** Shell large, umbilicate, lip with a small tooth at its 

 base ; sometimes also with a small parietal tooth. 



2. Ulostoma, Albers. Shell large, globosely depressed, 



aperture semicircular, lip tuberculateiy toothed at base. 

 Horn color, sometimes banded with rufous. 



Alleghany Mountains, from Vermont to Tennessee, and west- 

 ward to the Rocky Mountains. 



*** Shell large, umbilicus covered or perforate, lip not 

 toothed ; with generally a small oblique parietal tooth. 



3. Mksodon, Rafinesque. Shell large, subglobose or orbicu- 



larly depressed ; aperture rounded lunar, the lip some- 

 times slightly dentately thickened at the base ; parietal 

 tooth, when present, small ; umbilicus either covered by 

 an expansion of the lip or partially covered. Generally 

 uniform pale horn color. 



10* 



