THE OYSTER. 



47 



To the first group belong tlie Common Oyster, and be- 

 tween thirty and forty other living species which are found 

 principally in warm and temperate latitudes. In the Polar 

 ocean none have been discovered, and in the hotter climates 

 they are most abundant, being found in large beds or banks 

 near the coast, and often attached to rocks and even to trees 

 which grow by the water, so that the accounts of some old 

 travellers who stated that they saw Oysters growing upon 

 trees, were not so false as many supposed them. 



The annexed figure is that of the Cock's-comb Ovster, 



Oatrea Crid'i-Galli, a native of the Indian Seas, and a very 

 remarkable shell, on account of its crooked or deeply indented 

 form; the specific name means cock's -crest. The Chinese 



AVindow Oyster, called Pldcuna Placenta, which we mav, if 



