WING SHELLS. ge 
from the shell—in the Zima hians to more than its entire 
length—and, by a vigorous opening and shutting of its 
valves, this shell flies through the water, its long, golden- 
red tentacles streaming behind. It also constructs a nest 
by covering itself with stones, shells, etc., connected by 
its byssus. The common Pecten is called the dancing- 
scallop (Fig. 57), from its curious movements, darting 
through the water and above it with the greatest ease. 
VALUE.—Indian ornaments and articles of food. 
Wing Shells (Aviculide).—The Meleagrina or pearl- 
oysters have obtained great prominence from their pearl- 
bearing properties. They come from Madagascar, Ceylon, 
Panama, etc. The pearls are formed of a pearly matter 
called nacre, secreted by the animal. Ifa grain of sand 
falls into the shell, the oyster envelops it with a pearly 
coating to smooth off the edges, and layer by layer the 
pearl grows. Imperfect pearls grow upon the sides of the 
valves, and are generally the attempts of the oyster to re- 
pel the advance of some boring parasite. 
Note.—One fishery in Ceylon recently produced $80,000 worth of 
pearls, to obtain which 17,000,000 oysters were brought ashore. The 
fisheries are under the government control. Mother-of-pearl is the 
pearly shell of certain oysters, and valued in decoration. In one year 
twenty tons of silver-tipped shells have been received at Liverpool 
from the Society Islands, thirty tons of black-tipped roe Manila, and 
340 tons of a smaller kind from Panama. 
Pinna.—These shells, common on many shores, are 
wedge-shaped and horny, the hinge delicate, the beaks 
forming a sharp peak. The foot is long and grooved. 
Over thirty species are known, and are found buried in the 
sand off shore. They attain a length of two feet. 
VALUE.—The Pinna has long been noted for its silk, which is the 
cable or byssus by which the shell attaches itself to the bottom. 
Gloves and stockings of Pinna-silk can be seen in the British Museum. 
Gloves so made cost $1.50 a pair, and stockings $2.75. 
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