182 BIVALVES. 



upper valve small and flattened, the other convex ; 

 inside pearly white, outside dull brown. 



Oysters are generally found with their lower 

 valves fixed to rocks or loose stones, and frequent- 

 ly to one another. Most of our rocky coasts 

 abound with these shells, but Essex and Suffolk 

 are chiefly celebrated for them. They are dredged 

 up by a kind of net, with an iron scraper at the 

 mouth, and are immediately stowed in pits formed 

 for the purpose in the salt marshes, which are 

 overflowed only at spring tide, and from which 

 sluices let the salt water escape, retaining a depth 

 of about eighteen feet. The water being stag- 

 nant, in warm weather it becomes green, and in 

 a few days the oysters acquire the same tinge ; 

 they are then held in much estimation in the 

 market, but they do not attain their greatest per- 

 fection under six or eight weeks. The boats em- 

 ployed in dredging for oysters are from 14 to 30 

 or 40 tons ; the fitting out of one of 20 tons costs 

 ^8150 ; there are upwards of 200 now employed, 

 and above 500 men and boys. The quantity of 

 oysters taken on these coasts in one season is com- 

 puted to be about 20,000 bushels, which are 

 chiefly disposed of in London. 



Oysters are not considered fit for the table till 

 they are about a year and half old, and the fish- 

 ermen know their age by the increase in the, size 

 of the distance which separate the circles of laminae 

 in the convex valve. When young shells happen 

 to be taken, they are always rejected and cast back 



