BIVALVES. 



CHAMA Hippopus.* 



Specific character. Shell equivalve, inequi- 

 lateral, thick, heavy, longitudinally ribbed and 

 muricated ;t posterior slope heart-shaped, 

 closed ; margin in front deeply sinuous ; the 

 colour is white or yellowish, with scattered red- 

 dish or purplish spots ; commonly about two 

 inches long, and three inches and a quarter in- 

 side, but it sometimes occurs double this size. 



It inhabits the East Indian ocean. 



GENUS. ARCA4 



ARK. 



Generic character. Shell bivalve, equivalve, 

 inequilateral ; form various, often oblong, some- 

 times orbicular; hinge with numerous small 

 sharp teeth in each valve, alternately inserted 

 between each other, arranged sometimes in a 

 straight, sometimes in a curved line. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The shells of this genus are very readily 

 known, by their numerous small teeth. Some 



* Plate IX figure 2. 



f Muricated, having little pointed knots, from the Latin murex 

 the sharp point of a rock. 

 { Plate IX. figures 4, o,.6. 



