To Mr. Titian R. Peale I am indebted for speci- 

 mens, and for the information which I have obtained 

 respecting its locality on the coast of the United 

 States. This gentleman obtained numerous perfect 

 specimens, and introduced into our collections in this 

 city, the only authentic individuals by which we 

 could claim it as a North American species. 



The figure is considerably reduced. 



PECTEN CONCENTRICUS. 



Tab. I. Jig. 2, 3. 



SPECIFIC CHARACTER. 



Shell suborbicular, with from 18 to 20 elevated, 

 rounded ribs, and numerous concentric wrinkles; 

 inferior valve slightly ventricose or gibbous towards 

 the umbo; ears large, and nearly equal. 



SYNONYME. 



Pecten CONCENTRICUS. Say, Journ. Acad. J^at. 

 Sciences, vol. 2, p, 259. 



Cabinet of the Acad. Nat. Sciences, No. 1157. 



OBSERVATIONS. 



The colour of the upper valve is generally brown, 

 with pale zones, and the lower valve yellowish with 



