CONCHOLOGY. 49 



within ; internal margin of the valves distinctly dentated or 

 crenulated. 



D. denticulata. The denticulated Donax. 



Species of which the posterior side is truncated ; furrowed 

 from the summit to the base. 



9. Capsa. Two species. 

 This genus was separated by Lamarck from the Donax 

 on account of the peculiarity of the hinge. 



Capsa laevigata. Capsa Braziliensis. 



C. IcBvigata. The smooth Capsa. 



Triangular, sub-equilateral, obsoletely striated transverse- 

 ly ; covered with a greenish yellow epidermis ; inside violet 

 towards the umbones. 



C. Braziliensis. The Brazilian Capsa. PI. 8, fig. 7. 



Shell elongated, covered with epidermis ; equivalve, close ; 

 the cardinal teeth reduced to one large sub-bifid tooth on the 

 right valve, placing itself between two very thin ones on the 

 left ; ligament external, on the short side. 



10. Crassina. One species. 

 Distinguished from the Crassatella by the position of the 

 ligament, and from the Venus by having only two teeth on each 

 valve ; one of them on the left valve. projects very slightly. 



C. Danmoniensis. The Devonshire Crassina. PI. 6, 



Solid, thick, sub-orbicular, sub-equilateral ; two very large 

 divergent teeth on one valve, and two very unequal ones on 

 the other ; regular parallel grooves and ribs ; covered with a 

 yellowish epidermis ; inside white ; margin broad and plain. 



FAMILY IX. 



CoNCHACEA. Seven genera. 



This family is divided into Conchae fluviatiles, fresh-water 

 shells, and Conchae marinae, sea shells. 



G 



