43 



Several fliells of this defcription were taken by Mr. 

 Laskey, in the Frith of Forth, and though they were all 

 confiderably worn, yet they were lufficiently perfe6l to leave 

 no doubt of their being the Dyfera, for by comparifon 

 with foreign fpecimens, they were found to differ in nothing 

 from fome of the varieties ; eVeli in the markings clofe to 

 the cartilage, and the purple margin about the hinge. 



It muft be admitted that foreign fpecimens confiderably 

 vary according to the opinion of various authors ; but thofe 

 in queftion are not unlike Chemnitz, fig. 289. . 



Shell ftrong, thick, fub-orbicular, compreffed, and flightly Compressa. 

 fulcatcd, or irregularly wrinkled: the colour is white, but Tub. '26. f, LI. 1. 

 is ufually covered by a thick yellowidi-brown epidermis : 

 wnho prominent, turning to one fide, beneath which is a 

 fmall, lanceolate, cordiform deprefiion. Infide fmooth, 

 white, with a large cartilage depreflion near each end, and 

 the margin is fmgularly flat, and broad, from which the ca- 

 vity fuddenly commences, but is not very deep : hinge very 

 flrong, with two large teeth in each valve, and a tranfverfe 

 tooth-like ridge in one, which forms part of the cordiform 

 depreffion. 



Communicate to us by Mr. Laskey, who found it on the 

 fhell bank, near Dunbar, and other parts of that coaft, not 

 uncommon of a fmall fize, rarely exceeding half an inch in 

 diameter ; but as a proof of their fuperior growth, we were 



F 2 favoured 



