OF THE UNITED STATES. 247 



Great numbers of this species are devoured by the 

 dusky duck {Anas obscura,) and perhaps by other 

 birds. 



NATICA, Lam. 



Species. 



i. N. *duplicata. Shell thick, sub- globose, ci- 

 nereous, with a black line revolving on the spire 

 above the suture, and becoming gradually diluted, 

 dilated, and obsolete in its course ; within brownish- 

 livid ; a large incrassated callous of the same colour 

 extends beyond the columella, and nearly covers the 

 umbilicus from above; umbilicus with a profound 

 sulcus or duplication. 



Greatest length about two inches. Greatest breadth 

 rather more. 



Inhabits the coast of the United States. 



Cabinet of the Academy and Philadelphia Mu- 

 seum. 



Very numerous upon almost the whole extent 

 of our coast. The spire in some specimens is much 

 more elevated than in others, and the duplication 

 within the umbilicus, is sometimes partially conceal- 

 ed by the projecting callous. 



In the collection of the Academy of Natural Sci- 

 ences, is a species from Candia, presented by Mr. S. 

 Hazard, which very much resembles this, but it dif- 

 fers in being destitute of the black line, and in having 

 the umbilicus partially covered from the side, leaving 

 only a linear, semicircular, lateral opening. Another 

 specimen from India strongly resembles it, and is 



