84 CONCHOLOGY. 



6. Spondylus. The thorny Oyster. Twenty-one species. 



The valves of this genus greatly resemble those of the 

 common oyster, but have ears, and are covered with long 

 recurved or straight-pointed spines. 



The lower valve is much larger than the upper, and has 

 foliaceous laminae, by which it is attached to the other sub- 

 stances. They are found in all seas of hot countries, but 

 particularly in the Indian ; they adhere to rocks, coral, &c., 

 oftentimes in large groups. 



The usual colours are red, purple, white, brown, or orange, 

 several of which are sometimes blended in the same shell. 



Shell solid, adhering, sub-regular, more or less spined, 

 sub-auriculated, inequivalve ; the right or inferior valve fixed, 

 much more excavated than the other, and having behind, at 

 the summit, a triangular face, which enlarges and elongates 

 with age ; hinge longitudinal, provided in each valve with 

 two strong teeth entering into corresponding cavities ; liga- 

 ment short, almost medial, partly exterior ; one sub-dorsal, 

 muscular impression. 



Spondylus gaedaropus. Spondylus costatus. 



S. Americanus. S. variegatus. 



S. arachnoides. S. longispineus. 



S. candidus. S. regius. 



S. multilamellatus. S. avicularis. 



S. coccineus. S. microlepos. 



S. crassisquama. S. croceus. 



S. spathuliferus. S. aurantius. 



S. ducalis. S. radians. 



S. longitudinalis. S. zonahs. 

 S. violacescens. 



S.gadaropus. The thorny red Spondylus. PI. 15, fig. 1. 



Upper valve red, under one white, with longitudinal striae 

 or ribs ; rough granulations, and somewhat tongue-shaped ; 

 rather short truncated spines. 



