57 



with about fifteen elevated teeth placed within the margin, 

 fix on one fide, and nine on the other, divided by a fmall 

 concave plate that projedls inwards. Create fl diameter a 

 quarter of an inch ; the length not quite fo much. 



This new, rare, and delicate fpecies of Ark is defcribed 

 from a perfect fpeciraen in the cabinet of Mr. Laskey, It 

 was found by that gentleman on the fhore near Dunbar. 



PECTEN. 



Pecten obsoletiis, Br. Zool. t. 61, f. 66. Obsoletws. 



Pecten IjEvis, Jest. Brit. p. 150. p^ 14p^ 



Ostrea obsoleta, Lw. Trans, viii. p. 100, 

 Ostrea laevis, Lin, Trans, viii. p. 100, t. 3, f. 5. 



The obfcurity in which this, the PeSlen lavis, and glaher 

 of Pennant, have been enveloped, by the very fhort and 

 indefinite defcriptions of tlie authors who have defcribed 

 them, demands a clofer inveftigation in order to extricate 

 them from their prefent confufion. Mr. Pennant obferves 

 that his ohjoletiis is fmooth, with eight obfolete rays ; and 

 his figure is rayed, not ftriated, and the rays nearly as large 

 as the intermediate furrows or deprefiions, but do not extend 

 quile to the umbo. Da Costa, who defcribes a 'Pedleii 

 under the title of parvus with reference to the obfoletus of 

 Pennant, fays, " with numerous fine clofe fet longitudinal 

 Jlri<s, and at irregular- intervals they rife much more promi- 

 nent into fome eight or ten rays, which are the obfolete rays 



H of 



