OSTREA OYSTER, SCALLOP. 175 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



This genus contains shells very different in 

 their general appearance, but united by the pe- 

 culiarity in the hinge, which is toothless, and 

 has an elastic 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 

 generally eared ; its surface is adorned with di- 

 vergent ribs, which proceed from the apices to 

 the circumference, where they terminate in a 

 scalloped margin. The shells of this division 

 usually display 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 gray or black. 



The Pectens are described as possessing asto- 

 nishing powers of locomotion, considering the 

 inferiority of their organization ; but dexterity 

 and ingenuity frequently compensate for natural 

 deficiency. They have the power of progressive 

 motion, both on land and in the water. When 

 the animal happens to be left on the shore by 

 the retiring tide, it opens its valves to their full 

 extent, and closing them with great muscular 

 power, is thrown forward five or six inches by a 



