15 

 LIMA. 



GENERIC CHARACTER. 



Shell nearly equivalved, more or less oblique, sub- 

 auriculated, gaping a little on one side ; beaks separa- 

 ted, and their inner surface everted. Hinge with 

 a fosset, partly external, receiving the cartilage. 



OBSERVATIONS. 



This genus belongs to the family Pectenidx, and is 

 most nearly allied to Pecten, from which, however, 

 the species are easily distinguished by the obliquity 

 of the shells and their separated beaks, and they are 

 altogether destitute of the varied and brilliant colours 

 of the Pectens. They have an inconsiderable byssus, 

 and the habits of the animal are much the same as 

 in the preceding genus. They are even more active 

 in swimming, their valves moving with greater ra- 

 pidity. The recent species are few, only six having 

 been described by Lamarck, who also describes five 

 fossil species, but De France enumerates eleven. 

 None has yet been found in a fossil state in this coun- 

 try: there occurs, however, a species of Plagiosto- 

 ma in the Green Sand of New Jersey, which may 

 readily, without close examination, be mistaken for 

 a Lima. 



In Europe, this genus occurs in the Calcaire gros- 

 slera, and fossils of the lias have been referred to it, 

 the generic relations of which are, at least, doubtful. 



