Pelecypoda. 123 



Comparison of Clam and Oyster. It will be noticed that 

 the hinge in the oyster is at one end of the shell. This 

 end corresponds to the anterior end of the clam. The 

 oyster shell can open but slightly. The shells are rougher 

 than those of clams. The green spot in the oyster is the 

 digestive gland (often improperly called the liver), and 

 not the digestive tube or its contents, as commonly sup- 

 posed. Oysters and other salt-water mollusks are often 

 left above water at low tide. 



Distribution of Oysters. Oysters are abundant along 

 the Atlantic coast, south of Cape Cod, and in the Gulf of 

 Mexico. In former times they occurred north of Cape 

 Cod, but are now rare. Other species are found on the 

 Pacific coasts and on the coasts of Europe, at the Cape of 

 Good Hope, in Japan, and Australia. Chesapeake Bay is 

 the center of the oyster industry, and the British market 

 is now largely supplied from our beds, as we have not only 

 the most abundant supply, but ours are the best in the 

 world. 



The Oyster Season. The common saying that oysters 

 are good only in months containing the letter " r," is partly 

 wrong and partly right. Oysters are good to eat at any 

 time of the year when freshly taken from the water. But 

 during their breeding season June to August they do 

 not bear handling so well, and are more likely to spoil. 

 It is more profitable, too, to leave them undisturbed at this 

 time, that they may increase enough to maintain their 

 numbers. 



The Shipworm. As the name implies, this mollusk is wormlike. 

 It sometimes becomes ten inches long and half an inch thick. It bears 

 a small bivalve shell at its larger end. It burrows in wood, doing great 

 damage to ship timbers, buoys, wharves, etc. The first stages of devel- 

 opment are like those of many other bivalves. If the larva cannot find 



