PUPA. 321 



ture except a small portion of the body whorl, where a 

 thin, testaceous deposit connects its two extremities ; 

 aperture lateral, nearly oval, deep, cup-shaped, and nai'- 

 rowing towards the throat, wliich is almost filled up by 

 projecting teeth ; white within ; teeth commonly four, 

 one of which, affixed to the^body whorl, commences 

 at the superior margin of the aperture, near the junction 

 of the lip and ultimate whorl, and runs backward and 

 downward into the aperture ; it is prominent, lamelli- 

 form, irregular, has one or more sharp, projecting points, 

 and is sometimes bifid ; another, thick and massive, is 

 situated deep in the throat, and marks internally the 

 place of the umbilicus ; and two others, projecting and 

 toothlike, are placed on the lip, and point towards the 

 centre of the aperture. 



Base of the shell, from the umbiKcus to the edge of 

 the aperture, compressed, forming a short and obtuse 

 keel ; umbilicus a little expanded, and slightly perforate. 



Length of axis three-sixteenths of an inch ; diameter 

 half of the length. 



Geographical Distribution. This is a common 

 shell in the northern range of States from Missouri to 

 Vermont. It is also plentiful at various localities in the 

 Middle States, and on both sides of the Ohio River. 

 Mr. Bartlett found it in Arkansas. 



Remarks. This common and well-marked species is 

 the largest hitherto noticed in this country. At what- 

 ever extremes of distance it may be found, specimens pos- 

 VOL. u. 61 



