MARINE MOLLUSCA OF THE UNITED STATES 105 



A. squamula, Linn. Gould, Invert. Mass., edit. 2, 206. 1870. 



I do not know this species ; it does not appear, from the de- 

 scription, to differ from A. glabra. 



Genus PECTEN, 0. F. Mailer. 

 Zool. Dan. Prodi - ., p. xxxi. 1776. 



Animal with the mantle quite open, its margins double, the 

 inner pendant like a curtain finely fringed ; at its base a row of 

 conspicuous round, black eyes, surrounded by tentacular fila- 

 ments; gills exceedingly delicate, crescent-shaped, quite discon- 

 nected posteriorly, having separate excurrent canals ; lips folia- 

 ceous ; palpi-truncated, plain outside, striated within ; foot finger- 

 like, grooved, byssiferous in the young. 



Unlike the oyster, this is an active animal, having the power 

 of rapid motion. There are nearly two hundred species; of world- 

 wide distribution, extending to 200 fathoms in depth. 



1. P. Magellanicus, Gmelin. Fig. 537. 



(Ostrea). Syst. Nat., 3317. 1790. 

 Pecten tenuicostatus, Mighels & Adams. Bost. Journ. Nat. Hist., iv. 41, 



t, 4, f. 7. Bost. Proc, i. 49. 1841. 

 Pecten fuscus, Linsley. Am. Journ. Sci., 1st ser., xlviii. 278. 1845 



(young). 

 Pecten brunneus, Stimpson. Shells N. E., 8. 1851 (young). 



Shell large, orbicular, inequivalve ; superior valve more convex, 

 dull-red, with very numerous radiating striae which are crossed 

 by minute subscabrous wrinkles; inferior valve nearly flat, whitish, 

 with the stria; less distinct ; beaks purple ; white within. 



Diameter 6-9 inches. 



New England, New Jersey, West Indies t 



This is our largest species, and one of the largest in the genus. 

 It is distinguished by the absence of ribs, the surface being only 

 marked by fine striae. Most American authors have adopted 

 Mighels' name because the species does not come from the Straits 

 of Magellan as supposed by Gmelin ; but this is mere supposition, 

 and I think it is preferable to retain the original name. It has 

 been considered a northern species, but in the collection of the 

 Philadelphia Academy are fine specimens dredged alive in Raritan 

 Bay, also specimens from "West Indies." 



