OF CONCHOLOQY. 39 



* Dentate. 



t Umbilicus covered. 



Mesodon albolabris, Say. 



VARIETY DENTATA. 



Plate 7, figure 6. 



This species not unfrequently develops a tooth on the parietal 

 wall, (see description under section **,) and in this state it 

 closely resembles M. exoleta, but may be distinguished by its 

 larger size, less convex body whorl, broader lip, more transverse 

 aperture, and generally lighter substance. 



The dentate variety of albolabris has been found in Maine, 

 Massachusetts, Pennsylvania, Ohio, Iowa, Illinois, Michigan, &c. 



1. Mesodon exoleta, Bincey. 



Plate 7, figure 8. 



Ventricose, suborbicular, whorls 5 — 6, convex, texture heavy, 

 suture well marked ; body whorl large and convex ; aperture 

 rounded, lip reflected, the parietal wall toothed ; umbilicus 

 covered by the extremity of the lip. Light horn color. 



Diam. 25, height 15 mill. 



New York to Georgia, west of the Alleghany Mountains, and 

 extending westward to Missouri. 



2. Mesodon dentifera, Binney. 



Plate 7, figure 9. 



Depressed, spire flatly convex, base well rounded, whorls 5, 

 delicately striate, suture distinct, but not deeply impressed ; 

 aperture wide, lip broadly reflected and covering the umbilicus, 

 parietal wall armed with a prominent tooth. Yellowish horn 

 color. 



Diam. 19 mill. 



Maine to Virginia, and westward to Ohio, inhabiting mountain 

 ranges and highly elevated ground. 



Readily distinguished from the former species by its more de- 

 pressed form, &c. 



