258 AMERICAN JOURNAL 



8. Gastrodonta suppressa, Say. 



Plate 4, figure 41. 



Convexly depressed, thin, spire flattened, shining, pellucid; 

 whorls 6, slowly increasing, minutely striate above, beneath 

 more flattened and smooth, suture moderately marked ; aper- 

 ture transversely semi-circular, callously thickened within at 

 the base, with two parallel lamellas ; umbilicus merely perfo- 

 rated, sometimes covered. 



Diam. 6, height 4 mill. 



Middle States and Ohio. 



Has one whorl less and is more depressed and smaller than 

 No. 1 ; sometimes there are three instead of two teeth. 



4. Gastrodonta interna, Say. 



Plate 4, figure 42. 



Convexly orbicular, reddish-brown, shining, covered above 

 with close, rounded, very distinct ribs, beneath smooth ; whorls 

 8, narrow, very slowly increasing, suture deeply impressed, 

 periphery slightly angled ; aperture transverse, narrow, within 

 thickened, especially at base, with two short lamellae near the 

 outer portion of the basal margin; margin extending to the axis 

 beneath, which is sometimes narrowly perforate, but frequently 

 closed. 



Diam. 6, height 4 mill. 



West Pennsylvania to Georgia, and westwards to Missouri. 



5. Gastrodonta multidentata, Binney. 



Plate 4, figure 43. 



Depressed, thin, yellowish horn-color, smooth, shining, pel- 

 lucid* whorls 6, slowly increasing, suture impressed; aperture 

 transverse, narrow, lip extending to the perforated axis, base 

 convex, thickened within the aperture, through which may be 

 seen two to four rows of 5 or 6 teeth each, radiating from the 

 axis towards the circumference, upon the base of the outer 

 whorl • teeth situated far within, and last row not usually visi- 

 ble from the aperture. 



Diam. 3, height 1| mill. 



Green Mountains, Vermont, North-east New York, Maine. 



Readily distinguished by the teeth and size of the shell. 





