Page:Natural History, Mollusca.djvu/252

240 Pearls are indeed produced by several genera of shells both bivalve and univalve, but the most precious are obtained from the species named Avicula margaritifera, which is a native of the Indian Ocean. On the coast of India and Persia numerous fisheries are established, which supply the markets of the world with precious pearls. Some of these have been carried on from very ancient times; that for example at Catifa in Arabia, which produced the celebrated pearl bought by Tavernier for 110,000l., is mentioned by Pliny.

AVICULA.

The most productive fisheries are prosecuted in the Persian Gulf, and on the coast of Ceylon; that of the Bahrein Islands, in the former locality, often produces pearls to the value of 90,000.l sterling in two months, the time in which it is prosecuted. This is free to all adventurers on payment of the