100 MYA. GAPER. 



which we have very little doubt is this species of a smaller 

 size, but which it has not been our good fortune to exa^ 

 mine. We consider it however as an interesting subject, 

 which may serve to establish or annul our suspicions as to 

 the distinctions we have made between this species and the 

 last. v. v. 



5. Mya Norwegica. Norway Gaper. 

 Wood, pi. 18. f. 4, 5. 



Shell thin, brittle, transparent, convex, oblong-oval, 

 white but not glossy, and covered when fresh with a fine 

 brownish white skin, marked with numerous fine regular 

 raised longitudinal strieg, and a few transverse wrinkles j 

 one valve rather smaller than the other, and as it were re- 

 ceived within it; the larger side rounded, the other or an- 

 terior side sloping from the beaks, and running in nearly 

 a straight direction to the end, where it is truncated, very 

 rugged, with the valves gaping and a little reflected; the 

 front margin produced and rounded: beaks prominent, 

 pointed, nearly central : inside richly nacred : hinge with 

 a rather oblique triangular striated cavity in each valve : 

 length three-quarters of an inch j breadth more than one 

 and a quarter. 



A fresh and perfect specimen of this rare shell was 

 dredged up off Exmouth, in the present summer, and is 

 now in the possession of Mr. Leasathorp, who obligingly 

 suffered us minutely to examine and describe it. It had 

 no decortication about the beaks, as mentioned in the spe- 

 cific character of Gmelin and Dillwyn, and which might 

 have originated in an accidental abrasion of the fine epi- 

 , dermis or pellicle. The longitudinal striae appear to be 

 formed by regular corrugations of its outer skin, which at 

 the smaller and gaping end enlarge into rough membrana- 

 ceous folds. From the Mya striata it is distinguished by its 

 greater convexity, the teeth, the produced and rounded out- 

 line of the front margin, and the narrowed truncated Qn4 

 which resembles that of the M. declivis. v. m. 



6. Mya convexa. Convex Gaper. 

 Wood, pi 18. f. 1. 



Mya declivis. Donovan, pi. 82. 



Shell 



