PLATE CI. 



doubted whether they are not in general indebted to age, accident, or 

 the peculiar qualities of the waters they inhabit, for those variations 

 i 1 general appearance that have been too frequently mistaken for cha- 

 racteristic differences of species. 



As the Mya: will fall uiiJer consideration more fully hereafter, vv^c 

 shall for the present contine our remarks to the shell before us, and 

 its very analogous kind, the "Nlya ovata of Dr. Solaiidcr. 



This has been considered by some as a mere variety of ovata, and 

 we confess our opinion is still wavering in assigning it a name and 

 character as a new species. The Mya ovata has been lately found 

 in the river Froome m Somersetshire, and likewise in the New River 

 near London. What are usually deemed its varieties are numerous, 

 but none of them can, we believe, be considered as distinct specie*, 

 except the present, which is certainly the most remote of any, if it is 

 really a variety of that species. The Mya ovata, in all its gradations, 

 seems somewhat more ventricose and ovate in its contour, than this 

 Shell ; and though the variations of the latter are considerable, we 

 have generally observed a sligtit depression, across the middle, 

 which causes the narrowest end to be rather flattened throughout, 

 and it is also rather more cuneiform or wedge-shaped at this end 

 than Mya ovata : to this we might perhaps adti, with some proprletv, 

 that the gaping beyond the hinge at the broadest end, is wider than 

 m Mya ovata. 



Whether this difference Is actually sufficient to form a distinct specific 

 character, and whether ii is constant in other shells of this kind, still 

 lemalns in some degree of uncertainty. Both this and the Mya ovata 

 mhabit the same Waters, for we have seen several specimens from the 



