MOLLUSCS. 



85 



have a considerable commercial value, as they are the source of the mother- 

 of-pearl used for buttons, knife-handles, and various ornamental purposes. 



The Pearl Islands in the Persian Gulf are said to produce the finest 

 pearls, but the Ceylon fishery is the largest and oldest. In America, the 

 fishery at La Paz, Lower California, stands first in importance, its fisheries 

 having produced pearls to the value of a quarter of a million dollars, and 

 shells worth as much more, in a single year. 



In Ceylon, during the fishing season, each morning a large fleet of 

 boats sets out for the pearl-banks, which lie about ten miles distant from 



Fig. 80. — Pearl-oysters (Meleagrina rnargaratifera) . 



the northern shore. Each boat has a crew of about twenty-five men, ten 

 of them being divers, who are divided into two gangs, — five resting while 

 the others are below. For each diver there is a rope with a large stone 

 sinker and a loop for the foot, while a large wicker basket to hold the 

 shells is fastened farther up on the rope. Each diver further has a sharp 

 knife to use against sharks in case his amulets prove of no avail. Arrived 

 on the beds, work soon begins. Placing one foot in the loop of the rope, 

 the diver is quickly lowered by the crew to the bottom. Here he works 



