BIVALVES -i-OSTREA. 57 



OSTREA. Oyster, Scallop, or Pecten. 



DESCRIPTION OF PLATE XIV. 



Div. I. — Fam. 1. Fig. 2. 0. ziczac 



Fam, 4. Fig. 1. O. pleuroneetes. 

 DiT. II.— Fam. 1. Fig. 4. O. varia. 



Fam. 2. Fig. 6. O. obsoleta.- 

 Dnr.IV — Fam. 2. Fig. 5. O. folium. 

 Div. V. ~ Fig. 3. 0. isognomon. 



Shell bivalve, generally with unequal valves, and slightly eared; 

 hinge without teeth, but furnished tvith an ovate hollow, and usu- 

 ally with lateral transverse grooves. 



THERE are no less than eighty-eight species in this 

 genus, which present considerable variety in beauty and 

 form. 



The Ostreae are divided into several classes : the 

 first and second (which are the most important) com- 

 prise the innumerable varieties of escallops or scallop 

 shells, and are distinguished from each other by the 

 proportion of their ears. The first is, for the most part, 

 composed of very elegant species ; their form is usually 

 regular, and their surface is adorned with elevated 

 divergent ribs, varying in number from five to forty, 

 which proceed from the tip of the beaks to the extre- 

 mity of the margins, there terminating in a scalloped 

 outline. 



The Scallops are usually equivalve, but a few, as the 

 O. ziczac, O. jacobaea, and others of the same family, 

 have invariably the upper valve flat, and the lower 

 convex. 



It is remarkable, that in many of the Scallops the color* 



