16 



oped shell of this species, that name may well be retained for 

 the species. It was therefore adopted in the Report on the 

 Invertebrata of Massachusetts, p. 192, fig. 123. Professor 

 Adams also applied to it the specific term albilabris, in Silli- 

 man's Journal, XL. 271, and in his Catalogue of the Mollusca 

 of Vermont in Thompson's History, a name suggested by the 

 late Dr. Ward. Some doubt still remains as to whether it be- 

 longs to the genus Pupa, or to Bulimus, as the animal has not 

 been described. 



This shell is so well known as to require no more particular 

 illustration. The lip, however, is not often equally reflected, 

 but is much narrowed near the junction of the outer portion 

 with the body whorl. There are also two or three deeply cut 

 lines running parallel and near to its margin. 



Mr. Say found his specimens in the North-West Territory, 

 and it is not uncommon in Massachusetts, Vermont, New 

 York, Maryland and South Carolina. 



Its foreign analogue is P. umbilicdta, Drap. 



Having recently had an opportunity, by means of one of 

 Chevalier's large microscopes, of tracing off greatly enlarged 

 figures of these minute shells, with great accuracy, I will now 

 review the species described in the former part of this paper, 

 and notice those points which were inaccurately stated, or 

 which need further illustration, and add such further informa- 

 tion as I may have since obtained respecting them. 



P. CORTICARIA. The single tooth which Mr. Say describes 

 as being on the pillar lip, should read on the transverse lip, to 

 correspond with his subsequent descriptions of species. In 

 the figure (Vol. III. pi. 3, fig. 19,) the body whorl is repre- 

 sented too long. I have received it from Worcester county, 

 Maryland. 



P. EXIGUA. In the figure of this shell (Vol. III. pi. 3, fig. 

 20,) the body whorl is represented proportionally too large. 

 Its length is .08 inch. The only additional locality from 

 which I have received it is Troy, N. Y. 



The animal is colorless, and has only two tentacular devel- 



