SOLEN. 253 



and the former subarcuated ; but, as both extremities are a 

 little attemiated, the ventral effects this by rising at each 

 end, and thus its general curve appears to exceed that of 

 the upper margin. The umbones are rather depressed than 

 otherwise, the beaks almost undefined, but not terminal ; 

 so that there is an anterior side, although a very small 

 one, it not being quite equal in length to the ligament, 

 which latter is not peculiarly depressed, and occupies about 

 a sixth of the entire dorsal outline. The front extremity is 

 remarkably well rounded, particularly below ; the posterior 

 termination is bluntly subtruncated. The front dorsal edge 

 is convex and moderately sloping. The hinge occupies a 

 very small space, and closely resembles that of legumen. 

 It consists in the right valve of a single small compressed 

 primary tooth, and an adjacent posterior sublateral lamina, 

 which is rather short, and obliquely projects beyond the 

 hinge-margin. In the left valve is a curved posterior sub- 

 lateral denticle, a somewhat conical front primary tooth 

 with a posterior inclination, and a large central compound 

 tooth (that of the immature shell, when viewed from above, 

 reminds one of a high-heeled boot), forming with the two 

 preceding ones receptacles for the opposing teeth, and con- 

 sisting of a small acutely pointed conical primary tooth, 

 and a short sublateral lamina on the same base. 



The length of one of our larger specimens, which is at 

 least of the average size, is an inch and a half; its ex- 

 treme breadth is three-eighths of an inch. 



The animal of Solen pellucidus, is of a lanceolate form, 

 and not so thick in proportion to the shell as the other 

 species of this genus. Its siphons are very short, of a 

 tawny or dull orange yellow colour, united to their extre- 

 mities, and fringed at their orifices. The foot is long, com- 

 pressed, and obliquely truncated at the extremity ; it is of 



