132 OSTRBA. 



Shell somewhat orbicular, flat, thin, semitransparent, 

 quite smooth and glossy, except a few faint transverse 

 wrinkles, white or pale grey, sometimes mottled with 

 brown j the valves nearly equal : ears unequal, one of them 

 very large, the other small, slightly striate longitudinally ; 

 inside glossy white : length half an inch ; breadth not quite 

 so much. 



From the plain variety of O. sinuosa it may at once be 

 distinguished, by the want of the very fine decussate striae, 

 with which that shell is always marked. 



At the time Captain Laskey recorded his O. similis, the 

 true characters of O. laevis and O. ohsoleta were not clearly 

 understood : and as the only distinction between his shell 

 and the O. laevis is the want of the striae towards the mar* 

 gin, at that time supposed to form one of its essential 

 marks, it can now only be considered as O. laevis. 



Western coasts, and North Britain : very rare. v. m. 



9. Ostrea tumida. Tumid Scallop. 



Shell somewhat orbicular, flattisb, glossy white, trans- 

 parent, quite smooth : valves equal, with the sides un- 

 equal, both of them rounded, but one of them produced : 

 beaks pointed, not quite central; hinge straight, with the 

 ears rather large, equal, and quite smooth ; inside white, 

 smooth, with a large chalky patch in the centre, the mar- 

 gin plain : length a quarter of an inch ; breadth rather more. 



A single specimen only of this shell has as yet occurred 

 to us, taken from the cavities of a large mass of the Ser- 

 pula complexa, and which was dredged up at Torbay. It 

 is entirely unlike any other species with which we are ac 

 quainted ; and in consequence of one of the sides being 

 more tumid or produced, the breadth somewhat exceeds 

 the length, v. v. 



10. Ostrea glabra. Mottled Scallop, 

 Montagu, pi. 28. f. 6. 



Shell rounded, thin, nearly smooth but not glossy, most 

 iminutely striate transversely, with, seven rounded and 

 slightly raised rays, mottled with rufous brown and yellow : 

 ears large, nearly equal, one of them reticulated, the other 

 onJv atriate, inside market! with twenty-two slender rr\j*, 



the- 



