132 MARINE PRODUCTS OF COMMERCE 



After about 6 minutes the net, filled with some 50 green and corrugated abalones, 

 is hoisted aboard. During his shift on the bottom the diver gathers from 30 to 40 

 basketfuls, each containing about 100 pounds of abalones, or, altogether, 1/2 to 

 2 tons. A few naked divers work in water up to 20 feet in depth, but it requires 

 6 men to take as many abalones as 1 man in a scaphander. 



The meat of the abalones is considered a delicacy by connoisseurs of seafoods. 

 Abalone "steaks" command a high price. 



Black, red, and green shells are obtained. In polishing these shells they are 

 first ground on an abrasive wheel until the desired colors are reached. The surface 

 is polished further by a felt wheel sprinkled with silicon carbide dust. Finally 

 it is polished with a wheel made of many layers of cotton on the edges of which 

 tripoli has been rubbed. A single shell yields as many as 15 pieces of mother-of- 

 pearl suitable for ornaments. Scimitar-shaped paper knives are often cut from 

 the shells. 



Japanese Mother-of-Pearl Fisheries. Although the pearl fisheries of Japan are 

 not extensive, except in a few localities, the aggregate yield has been considerable. 

 The "awabi," or "ear-shell" {Haliotis gigantea), found on the coast of Japan, 

 Korea, etc., furnishes many pearl forms, although this species is much smaller than 

 the California abalones. Its smooth, nacreous surface is unfortunately lessened in 

 value by the size of the marginal perforations. Its opalescent tints adapt it well 

 for the manufacture of certain types of buttons and buckles; but it is chiefly used 

 for inlays, its fine texture and beautiful coloring recommending it highly for this 

 purpose. 



The Indian Chank Fisheries. About 2,500,000 chank shells are taken annually 

 in India where that mollusk (Turbinella pyrum, Linn.) is considered sacred by 

 the Hindus. The chief fisheries are located at Tinnevelly, Ramnad, Travancore, 

 Kathiawar, Ceylon, and along the Carnatic coast. The shells are taken principally 

 by native divers, although in shallow water some are taken with hooks. This 

 fishery is ancient, dating back more than two thousand years. The chank shells 

 are manufactured into bangles and other ornaments for Indian trade. 



Classification of Shells 



Size and Quality. The various kinds of pearl oyster shells have been thus classi- 

 fied in the English market: 



Certain special designations refer to the source, as for example: 

 "Ceylon" indicates shells of the Margaritifera vulgaris Jameson, fished in the 

 Gulf of Manaar near Ceylon. These shells are brilliant and do not exceed 3/2 

 inches in length; they are thin, and the valves are prolonged into posterior wings 

 at the hinge. The nacreous stratum is very thin. 



"Mergui" refers to shells of the Margaritifera, fished in the Burmese Archi- 

 pelago of Mergui. Here are also secured shells of the Turbo marmoratus which are 

 green and therefore called green snail mergui. 



