CHAMA CLAM OR CLAMP. 169 



supposed external resemblance of the Spondylus 

 to the oyster it has been called the Thorny 

 Oyster; its scientific name is derived from the 

 Greek <nrovSv\os (spondulos) the head of an 

 artichoke. 



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 

 laminated or tongue-shaped, 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 



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 recurved ; 

 form various. 



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



15 



