224 ANCYLUS. 



7. ANCYLUS RIVULARIS, Sa7j. 



Hald. Monog. p. 4, t. 1, fig. 1. 



Extensively distributed through the North- 

 ern, Middle and Western States. 



8. ANCYLUS TARDUS, Say. 



Hald. Monog. p. 7, t. 1, f. 3. 



Maine, Vermont, New York, District of Co- 

 lumbia, Indiana. 



9. ANCYLUS CALCARIUS, DeKay. 

 Plate 2, fig. 3, 4. 



Shell conic, calcareous, opaque. Apex not 

 central, moderately prominent ; aperture oval, 

 entire; the curves on the longest sides dis- 

 similar. In very minute specimens, the edges 

 somewhat everted. Epidermis rufous, extend- 



(18) 



