60 

 S P O N D Y L U !S. 



(Plate VII. Fig. «.) 



Shell inequivalve, rough. Hinge having two 

 recurved teeth with an intermediate hollow ; some- 

 times eared. (Fig. 5.) One of the valves convex 

 and thick, the other flatter. 



The intermediate sinus contains a connecting 

 cartilaoe, as in some other oenera. The lower of the 

 two valves of this singular shell is, in many indi- 

 viduals of the first species, G(zdaropi(s, produced 

 towards the apex into a projecting beak, one side of 

 which is excavated so as to leave a flat space j)er- 

 pendicular to the hinge. Through this the cartilage 

 is continued in a curvilinear direction to the very tip. 

 The aj)pearance is that of an imperfect specimen, 

 having one of the apices artificially mutilated. 

 The surface is always coarse and rough, tuber- 

 culated or spinous, and more or less pectinated. 

 With the exception of the strong and well-defined 

 teeth which are peculiar to this genus, and which 

 are totally wanting' iu that of Ostrea, the affinity 



