Читать книгу The Book of the Pearl. The history, art, science, and industry of the queen of gems онлайн

102 страница из 197

Yet another subspecies, the M. m. mazatlanica, occurs on the coasts of Panama and Mexico, and especially in the Gulf of California. This is likewise green-edged, and the exterior color is yellow or light brown. This shell has been marketed in quantities since 1850, and is known in the mother-of-pearl trade as “Panama shell.” It is smaller than the Australian species, specimens rarely exceeding eight inches in diameter. It yields a large percentage of the black pearls that have been so fashionable in the last fifty years.

Since 1870, the largest pearls have been found mainly in a very large species of pearl-oyster, Margaritifera maxima, obtained off the north and west coasts of Australia, among the Sulu Islands, and elsewhere in the Malay Archipelago. In the fisheries for this species, the mother-of-pearl is the principal object sought, and the pearls are obtained incidentally. It is the largest of all the members of this family, reaching in exceptional cases twelve or thirteen inches in diameter, and weighing upward of twelve pounds; while the Ceylon oyster rarely exceeds four ounces in weight. So marked is this difference, that the Australian species is often designated the “mother-of-pearl oyster,” and the Ceylon species the “pearl-oyster.” Jameson notes that it differs from the Margaritifera margaritifera, its nearest competitor in size, in its much longer hinge, its shape, its lesser convexity, and in its color and markings. As described by him, the color ranges from pale yellowish brown to deep brown, with traces of radial markings of dark brown, green, or red in the umbonal area. In its marginal region, the shell is marked by a series of circumferential lines about one third of a millimeter apart.