38 GO'i^GRYLlA—DITHYRA. 11. 



Named from Mr. Swainson, of Elm Grove, near Liverpool, long 

 known in the annals of British Conchology, 



decussata. 

 3. 



Sphenia testa ovatd decussatim striata, margine undato. 

 Shell oval, with decussate striae, and the margin undate. 

 Mya decussata Montagu, Suppl. p. 20, tab. 28, fig. 1. 



Pennant, Brit. Zool. iv. p. 167. 



Wood, Conch, p. 99. 



Dillwyn, Descript. Catal. p. 46. 



Turton, Conch. Diet. p. 102. 

 Taken in the Frith of Forth, by Capt. Laskey. 



We are unacquainted with this shell, but conclude from Mon- 

 tagu's description, that it falls into this genus. It is said to be 

 half an inch long, and rather more in breadth, oval, white, undulate 

 at the margin, with irregular transverse ridges which are crossed 

 by regular longitudinal striae, forming tubercles at the anterior end. 

 In the hinge a broad erect tooth in one valve, and a projecting plate 

 with a small indentation in the other. 



II. COB.BVLA—BRUGUIERE. 



Testa subtrigona, inoequivalvis, inaquilateralis, clausa. Cardo valva 

 sinistroe dente conico cum foveold adjectd, valvce dextree dente cock- 

 leariformi cum foveold : lateralibus nullis. Ligamentum internum. 



