12 LIMNEA EMARGINATA. 



deep emargination, as exhibited in figures 3 and 

 7 in wanting the fold upon the columella, and 

 in having umbilics of the same character. 

 Should the latter prove to be a distinct species, 

 I propose to call it L. serrata; its distinguish- 

 ing characters being the elevated lines, and the 

 undulated peritreme. It is probably included 

 by J. D. C. Sowerby among the new species 

 discovered by Dr. Richardson. 



EXPLANATION OF PLATE 2. 



Figures 4 and 5 are copied from an authentic specimen in 

 the Academy's collection: 1,2, 3, represent a more elon- 

 gated variety, drawn from an imperfect specimen; and 6, 

 7, 8, a shell which is more ventricose, and is marked with 

 a few transverse elevated lines upon the body whirl. 

 These two shells, with many other species, were brought 

 from the North-west Territory by Mr. R. C. Taylor, who 

 gave them to Mr. Conrad; to whom I am indebted for the 

 freshwater univalves contained among them. 



