possess the power of locomotion, either in the wa- 

 ter, or when left by the tide, or cast by the waves 

 on shore, as by a rapid action of the valves, they 

 are enabled to travel down the sloping sands of the 

 beach, and by the same means they move with ce- 

 lerity in the water, or rise at pleasure to the surface. 



It might appear to almost every one conversant 

 with the subject, that this genus was too natural 

 to admit of any dismemberment ; but Schumacher, 

 a Danish naturalist, has ventured to introduce 

 into his system of Conchology two genera, formed 

 out of the present one, under the names of Amu- 

 sium and Janira, but they are, like many other 

 genera which he has instituted, founded upon tri- 

 vial distinctions. 



To the present genus belongs the beautiful shell, 

 well known as the scallop of the pilgrims. 



Several species, two of which are among the 

 largest of the genus, occur in a fossil state in the 

 Tertiary, or older Pliocene of Lyell, in Maryland 

 and Virginia. 



PECTEN MAGELLANICUS. 

 Tab. I, fig. 1. 



SPECIFIC CHARACTER. 



Shell large, orbicular ; superior valve dull red, 

 with very numerous radiating striae which are 

 crossed by minute subscabrous wrinkles ; inferior 

 valve nearly flat, whitish, with the striae less dis- 

 tinct ; beaks purple ; within very entire. 



