176 HELICID^E. 



nearly a continuous circle ; umbilicus large, exhibiting 

 all the volutions. 



Extreme transverse diameter one-tenth of an inch. 



GEOGRAPHICAL DISTRIBUTION. Inhabits all the At- 

 lantic States from Maine to South Carolina, and from 

 Vermont to Council Bluffs on the Missouri. It is com- 

 mon in the neighborhood of Boston, and so common in 

 Vermont that Prof. Adams states that he has taken 

 eleven hundred in an hour. 



REMARKS. I have recently received from Dr. Grif- 

 fith specimens with the raised striae, or parallel ribs, 

 taken in gardens in Philadelphia. It is the variety 

 which Miiller described as Helix costata. 



Though very minute, it is a beautiful species ; and its 

 form, which is seen to most advantage by the aid of a 

 magnifying glass, resembles very much that of Cyclo- 

 stoma volvulus. It is commonly found under stones. It 

 is thought by some to have been introduced from 

 Europe ; but I am of opinion that it is a native species. 

 It does not seem possible that so small an animal, if 

 naturalized near the sea-shore since the arrival of Euro- 

 peans, should have been able to penetrate to the remote 

 points in the interior of the continent where it is now 

 found. 



