SPONDYLUS THORNY OYSTER. 171 



transverse lines ; margin crenated ; colour grey, 

 or ivory white, variously marked with chesnut 

 brown spots, the area and areola are of the same 

 colour as the spots ; diameter about at inch. 



Found on the shores of America, and the East 

 Indies. 



Genus. SPONDYLUS.* Pfontf, Spandyli. 



THORNY OYSTER. 



4 



Generic Character. Shell bivalve, inequivalve, 

 inequilateral, fixed, strong, solid ; surface coarse 

 and rough, with either lamellar or subulate 

 spines ; the hinge has two strong recurved teeth 

 in each valve, with an intermediate sinus for the 

 ligament ; the lower valve is convex, and is 

 produced at the apex into a projecting beak which 

 appears as if it had been sliced off by a sharp 

 instrument, presenting a triangular flattened sur- 

 face, having a groove which receives the decaying 

 part of the Mgament. The shell is often eared. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The shells of this genus are remarkable, not 

 * Plate VIII. figures 9, 10. 



