PUPA. 333 



and two upon the laljial margin ; lip thickened, not 

 reflected ; umbilicus a little open. 



Lengtli of axis one-sixteenth, diameter one-thirty- 

 second, of an inch. 



Geographical Distribution. A mdely spread spe- 

 cies. Noticed hitherto near Baltimore, Albany, and Bos- 

 ton, on the bark of oak trees, in groves. Also by Mr. 

 Haldeman in Eastern Pennsylvania, on damp ground 

 near springs. Mr. Stimpson has found it most abundant 

 in heaps of stones, in open fields. 



Remarks. A very pretty species, intermediate be- 

 tween P. ovata and P. milium, both of which it resem- 

 bles in the character of the aperture ; but it differs from 

 the former in the less developed character of the last 

 whorl, and from the latter in size. When placed in a 

 moist place the animal moves with great activity ; but 

 in a dry place it speedily withdraws into the shell, and 

 attaches itself firmly by the aperture. In winter, it is 

 always found thus attached to sticks and stones by a 

 thin, calcareous epiphragm, which often remains upon the 

 resting-place when the shell is torn away. 



VOL. II. 84 



