OSTREA EDULIS. 139 



Ostrea edulis; Lister, Hist. Conch. 1. 193-4 ; Da Costa, Brit. Conch, t. 11, f. G; 

 Lin. Trans, vi. t. 18, f. 9, 10; Pennant, Br. Zool. i v. 225 ; Syst. Nat. Gmel ■ 

 p. 3334 ; Brotun, Illust. t. 31, f. 19. 



The shell of the eommon Oyster is more or less orbicular, but 

 subject to considerable variation in size and form. It is composed 

 of two unequal valves, one of which is smaller, flat, and entire ; 

 the other, adhering to marine bodies, is larger and convex. The 

 valves are rough externally, of a dull brown colour, often dis- 

 torted, plicated at the edges, and of a pearly white within. There 

 are no teeth in the hinge, but an elastic ligament placed in an 

 oblong furrow under the beak. 



The Oyster inhabits the European and Indian Oceans. It is 

 found in great abundance on many of the British shores, which 

 were famed from the earliest times for producing the best Oysters, 

 and from whence they were sent in quantities to supply the stews 

 of ancient Rome. Thus Juvenal, in satirizing a Roman epicure, 



says ; — 



Circseis nata forent, an 

 Lucrinum ad saxum, Rutupinove edita fundo, 

 Ostrea, callebat primo deprendere raorsu. 



Colchester and Melton are the places most celebrated for oysters, 

 and, when taken, they are generally laid down near the shore in 

 layers, and fed before being brought to market. At present, the best 

 Oysters on the British shores are said to be found at Purflect, and 

 the worst near Liverpool. 



Medical Uses. — Oyster-shells have long been admitted into the 

 pharmacopoeia, on the supposition that they afford a variety of carbo- 

 nate of lime, more free from gritty particles and purer than prepared 

 chalk. They consist of alternate layers of carbonate of lime and a 

 portion of animal matter, probably coagulated albumen. Oyster- 

 shells are employed as antacids \ but they do not seem to possess 

 those virtues in any greater degree than carefully prepared chalk. 

 The Oyster, particularly in its raw state, is wholesome and nutri- 

 tious, and is frequently taken as a light restorative aliment by the 

 feeble and consumptive. The cockle, the mussel, and the snail, 

 arc similar in alimentary properties to the Oyster, though greatly 



