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[73] 



******* Shell small, depressed and ribhed-striate above, 

 vnany-ivliorled ; perijiliery geverally carinate ; convex 

 beneath, showing several luhorls ; aperture with a 

 V-shaped parietal tooth. 



t Aperture tridentate, base exhibiting one and a half to two- 

 ivhorls. 



D^DALOCHiLA, Beck. Shell small, depressed, ribbed- 

 striate, periphery angulate, below convex, showing more 

 * than one, sometimes nearly two, whorls, with a minute 

 central perforation; lip auricular, frequently expanded,, 

 the place of the teeth being marked externally by scro- 

 biculations ; parietal tooth V-shaped, joined by a raised 

 callus with the extremities of the lip. 



-Southern States, Mexico, Guatemala, Cuba, &c. 



X Shell planorboid, many-whorled ; aperture with a V- 

 shaped tooth, but no lip teeth. 



PoLYGRA, Say. Shell planorboid, many-whorled, whorls 

 narrow, ribbed above, periphery angulate ; aperture 

 small, subtrigonal, with a V-shaped pariet;il tooth, joinedi 

 by a raised callus to the extremities of the lip ; below 

 plane, showing several whorls, with a narrow umbilicus- 

 Horn color. 



Gulf States and West Indies, also South America. 



VALLONIA, Risso. 

 1. Vallonia minuta, Say. 



Plate 7, figure 2. 



Spire depressed, convex, whorls four, the last rapidly increas- 

 ing and spreading at the mouth ; thin, transparent, very min- 

 utely striated, or sometimes distantly costate ; aperture orbicu- 

 lar, lip large, well rourfded ; umbilicus large. Light horn color; 

 with generally a greenish tinge, lip white. 



Diam. 2-5 mill. Cc\\:''.a:S:. C^w 



Maine to South Carolina, and westward to the Rocky Moun- 

 tains. 



This species was described many years ago by Mr. Say, and 

 his species has since been recognized as distinct bj several con- 



