130 HELICID^E. 



the lip, the plane of the aperture making a considerable 

 angle with the plane of the base of the shell : pillar 

 lip with a prominent, white, tooth-like process placed 

 obliquely to the axis of the shell ; lip white, widely re- 

 flected, and sometimes grooved on its face ; exterior of 

 the reflected lip yellowish ; umbilicus exhibiting only 

 one volution, partially covered by the reflected lip where 

 it unites with the base of the shell. 



Extreme transverse diameter one inch, ordinarily 

 three-fourths. 



GEOGRAPHICAL DISTRIBUTION. Inhabits plentifully 

 all the States from New York to Missouri, and from 

 South Carolina to Arkansas. It is very common in the 

 country bordering on the Ohio and Mississippi Rivers, 

 and though sometimes found, is not common in the New 

 England States. 



REMARKS. This species bears a strong resemblance 

 to H. albolabris, with which it is sometimes confounded. 

 It has, however, striking specific characters, which are 

 never wanting, and which will enable one always to dis- 

 tinguish it. These are, the partially closed umbilicus, 

 and the tooth on the pillar lip. The yellow color on the 

 posterior part of the reflected lip is also a very constant 

 character ; this is derived from the mantle of the animal, 

 which, in a state of rest, frequently overlaps the margin 

 of the aperture. It is a smaller shell than H. albolabris, 

 and more convex, and the plane of the aperture makes 

 a much larger angle with the plane of the base. 



