262 HELICID^. 



Greatest transverse diameter one-eightli of an incli, 

 usually less. 



Geographical Distribution. Inhabits the North- 

 ern, North-eastern, and Middle States, and those border- 

 ing upon the Ohio River. Common in Vermont. 



Remarks. This peculiar shell is distinguished by its 

 discoidal form, greenish color, the fine revolving lines 

 upon its whorls, and the singular teeth which are placed 

 in the interior of the outer whorl. These teeth are 

 arranged in pairs, on the external side of the parietes of 

 the cavity, one of each pair being on the superior and 

 one on the inferior part of the whorl. They are prominent, 

 white, and conical, and may be discovered through the 

 semi-transparent shell. One pair is so near the aperture 

 as easily to be seen, on looking into it ; the other is dis- 

 tant nearly one-half a volution from the lip, and is of 

 course invisible except through the shell. At least one 

 pair wiU be found to exist in every specimen, when care- 

 fully sought for : in one instance, I noticed a third pair 

 still further within the whorl. 



Noticed under the bark, or in the interstices of wet 

 and decaying wood, and under layers of wot leaves, and 

 stones, in damp places, in forests. 







