1.12 



lion in which it is found : fome have very flrong, thick, 

 ponderous fiiells ; others are thin, with membranaceous 

 plates or huninx, obfcurely and irregularly ftriated. 



A pretty variety is found in Salcomb bay in DevonJJiire, 

 with a very thin fliell, with large membranaceous plates, 

 wrinkled into irregular, interrupted ribs : the upper valve 

 flat, or rather concave on the top, with a corneous mar- 

 gin, half an inch broad, extremely thin and brittle: the 

 lower valve convex, clouded with pale purple, particu- 

 larly round the mr.rgin. Thefe are called Rock oyjlers, 

 and vary fo much from others, taken from a different part 

 of the fame bay, that they appear like a diflinft fpecies ; 

 and are very unlike thofe which are cultivated for the 

 London markets ; they are generally of an orbicular fliape ; 

 with the umbo pointed, and central. Diameter about three 

 inches and a half. 



It is the nature' of oyjlers in general to have the lower 

 valve fixed to rocks, or loofe flones, and frequently to 

 each other; but this is not the cafe with the variety jufl; 

 dcfcribed, in confequence their fhape is more regular. 



The appellation of Rock oyjicr feems to be given it by 

 the fifliermen, becaufe they are taken on rockey ground. 



For an account of the taking, breeding, and manage- 

 ment o^ oyjlers, in order to fupply the tables of the luxu- 

 rious, we refer our readers to the BritiJIi Zoology ; Dale's 

 Jlijlory of liarzcich ; and Da Costa's BritiJIi Conchology ; 



which 



