OSTREA OYSTER, SCALLOP. 179 



inequivalve, inequilateral, more or less eared ; 

 hinge without teeth, having an ovate sinus, in 

 which is fixed an elastic cartilage, and generally 

 lateral transverse grooves. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



This genus contains shells very different in their 

 general appearance, but united by the peculiarity 

 in the hinge, which is toothless, and has an elas- 

 tic cartilage inserted into a sinus. It may be 

 divided into two families, the Pecten or Scallop, 

 and the Oyster, which are separated by very 

 marked distinctions. 



The Pecten is of a regular orbicular form, 

 and eared ; its surface is adorned with divergent 

 ribs, which proceed from the apices to the cir- 

 cumference, where they terminate in a scalloped 

 margin. The shells of this division usually dis- 

 play brilliant colours. 



The second division contains the species more 

 or less resembling the common oyster ; these 

 shells are irregular in their form, have a rugged 

 and laminated exterior, with one valve more con- 

 cave than the other, are generally without ears, 

 and their colour is grey or black. 



The Pectens are described as possessing asto- 

 N 2 



