152 l/NIVALVE SHELLS 



is also referred to as the same, I conclude that two 

 distinct species have been confounded together under 

 the common name of punctata; certainly the charac- 

 ter from which this name was taken, is never present 

 on our shell. Specimens have been subsequently 

 found by Dr. Thomas M'Euen, near the fails of 

 Niagara. 



3. H. *palliala. Shell depressed, with elevated 

 lines, forming grooves between them; epidermis fus- 

 cous, rugose with very numerous minute tubercu- 

 lous acute prominences; volutions five, depressed 

 above, beneath rounded, forming an obtuse angle 

 exteriorly, which is more acute near the termination 

 of the labrum ; umbilicus covered with a white cal- 

 lous ; aperture contracted by the labrum; labrum re- 

 fleeted widely, white, two profound, obtuse, sinusses 

 on the inner side above the middle, forming a promi- 

 nent distinct tooth between them, and a projecting an- 

 gle near the middle of the lip; labium with a large, 

 prominent, white tooth, placed perpendicularly to the 

 whorl, and obliquely to the axis of the shell, and 

 nearly attaining the umbilical callus. 



Inhabits Illinois. 



Length of the column 7-20 of an inch. 



Greatest breadth, four-fifths of an inch. 



Yar. a. A very prominent acute carina ; destitute 

 of minute prominences. Inhabits Ohio. Breadth 

 nearly 1 inch. 



