54 GENUS V. SOLEN. 



or umbo is in general small and flat ; it is always close to the 

 cartilage, whether that be near to the centre or to one end. 



There are a few shells placed here by Linnaeus, and more 

 by Gmelin and Turton, which would evidently be better re- 

 moved, as Solen sanguinolentus, huUatus, anatinus, &c., since 

 the teeth do not agree with the generic definition. 



Linnaeus has described 11 species, Gmelin has added 12, 

 and Dr. Turton none. In all, 23. 



Lamarck has divided this genus into two, as follows : 

 Sanguinolaria. Shell transverse, the upper edge arclied, a 

 little gaping at the extremities ; the hinge teeth two, 

 approximating and articulating on each valve (see Solen 

 sangiiiiiole7itus, pi. 2. /. 14). 

 Solen. Shell transverse, the upper and lower edges nearly 

 straight ; beaks not projecting, gaping at both ends ; 

 hinge teeth single in each valve, or double in one ; carti- 

 lage external (see Solen Vagina, pi. 2. f. 13). 



