20 



IV. MYSCA. 



Shell bivalve, transverse, equi valve, inequilateral, a 

 little open at the sides. Hinge with a transverse 

 crenate primary tooth, which in one valve is di- 

 vided into two lobes : lateral teeth at the anterior 

 side only, laminar, transversely elongated, and 

 double in one valve, without the terminal depres- 

 sion. Ligament external. 



10. Mysca Batava. Shell oblong, rounded at both 

 ends, with the beaks rugged and warty. 



Mysca Batava. Turton^ Dith, j). 244. 

 Mya Batava. Wood, p, 103. ^. 19./. 1, 2. 

 Mya Pictorum. Montagu, p. 36. 



Shell an inch long, and two broad, greenish-brown, 

 without contraction in the front margin, by which 

 it is chiefly distinguished from the M. Pictorum ; 

 inside dark-bluish. 



In the river Kennet, above Newbury. 



11. Mysca Pictorum. Shell somewhat angular and 

 pointed at the anterior side, with the front margin 

 a little contracted, and the beaks rugged and warty. 



