CHAMA CLAM OR CLAMP. 173 



SPONDYLUS Gcedaropus* 



THORNY OYSTER. 



Specific Character. Shell slightly curved, 

 spinous, varies greatly in colour, size, and the 

 form of the spines, the latter are generally lam- 

 inated or tongueshaped, sometimes foliated ; the 

 colour varies from saffron, to orange and scarlet ; 

 the size is about two inches in diameter. 



It is found adhering to rocks in the Mediter- 

 ranean. 



Genus CHAMA.f (Plural, Chama.) 



CLAM OR CLAMP. 



Generic Character. Shell bivalve, solid exte- 

 rior usually coarse ; hinge has a gibbous callo- 

 sity inserted obliquely into a corresponding 

 sinus in the opposite valve ; this callosity or 

 tooth is either simple or crenated ; beaks re- 

 curved; form various. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



This genus, as it stands in the Linnaean classi- 

 fication, contains twenty-six species, but some 



* Plate VIII. figure 9. t Plate IX, figures 1, 2, 3. 



