54 CONCHYLI A— D/THYi?^. 17. 



Mactra alba. Linn. Trans, vi. tab. 18, fig. 9 to 12. 



Mus. nost. English and Irish coasts. 



^ Shell more than half an inch long, and three quarters broad, 

 thin flat, glossy white, a little angular at one of the sides when 

 full grown : beaks not quite central : inside smooth glossy 

 white. 



17. AGm A— TURTON. 



Testa, transversa, ovata, cequivalvis, inaquilateralis, latere antico 



hiante. Cardo dente unico erecto conico penctrante in utrdque 



valvd : lateralihus nullis. Ligamentum externum. 

 Shell transverse, oval, equivalve, inequilateral, open at the anterior 



end. Hinge with a single erect conic penetrating tooth in each 



valve : lateral teeth none. Ligament external. 



purpurea. AgiNA. 

 I. 



Tab. nost. 4, fig. 9. 

 Mya purpurea. Montagu, Te.st. Brit. Sujipl. p. 21. 

 Mils. nost. From rocks in Torbay. 



