OF THE UNITED STATES. 263 



series of wrinkles, it approximates to A. morio of 

 Leach, but (lifters from it in magnitude, and in being 

 radiated with whitish lines. I have a specimen from 

 the West Indies, which corresponds very well with 

 this, but as it is a much older shell, it is of a much, 

 darker colour, and the radi are interrupted into ab- 

 breviated lines. 



A valve of an adult shell, also occurred on the 

 southern coast, but so much worn by attrition, that 

 its superficial characters are destroyed. 



MYTILLUS, Lin. Lam. 



Species. 



1. M. ^cubitus. Shell oblong, striated with ele- 

 vated, subglabrous lines, which are smaller on the 

 anterior side ; anterior edge linear, or slightly con- 

 cave ; posterior edge ascending from the base in a 

 right line to a prominent angle, which is rather be- 

 hind the middle of the shell, from which it descends 

 by a concave line to the obliquely and very obtuse- 

 ly rounded tip ; colour yellowish, polished and some- 

 what fascia ted with green or brownish, which dis- 

 appear on the anterior margin. 



Length one and one-fifth of an inch. 



Breadth half an inch. 



Inhabits the coast of the United States. 



Cabinet of the Academy and Philadelphia Mu- 

 seum. 



This species, seems to be most closely allied to 



