WING SHELLS. 55 



from the shell in the Lima 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 (Avbulufo).T\ie 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. If a 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 gro;v 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 from 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. 



