MARINE MOLLUSCA OF THE UNITED STATES 195 
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, O. F. Miiller. 
Zool. Dan. Prodr., 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. MagceLuanicus, Gmelin. Fig. 537. 
(Ostrea). Syst. Nat., 33817. 1790. 
Pecten tenuicostatus, Mighels & Adams. Bost. Journ. Nat. Hist., iv. 41, 
teieie  BOst. Proc... 49) g1841c 
Pecten fuscus, Linsley. Am. Journ. Sci., Ist ser., xlvili. 278. , 1845 
(young). 
Pecten brunneus, Stimpson. Shells N. E., 8. 1851 (young). 
Shell large, orbicular, inequivalve ; superior yalve more convex, 
dull-red, with very numerous radiating strize which are crossed 
by minute subscabrous wrinkles; inferior valve nearly flat, whitish, 
with the striz less distinct; beaks purple; white within. 
Diameter 6-9 inches. 
New England, New Jersey, West Indies? 
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 striz. 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.” 
