Murex, a genus of gasteropod mollusks, found in almost all temperate and tropical seas at depths varying from 25 to 60 fathoms. About 200 living species are known, and 160 fossil, chiefly belonging to the eocene formation. Some of the species are remarkable for their very long and slender beak, along which the canal is partly closed. The shells are ornamented with three or more longitudinal ridges, from which sometimes proceed rows of long pointed spines, which are removed by the animal when they interfere with its growth. The murices are particularly interesting from their having been the source of the famous Tyrian dye. It is said that heaps of broken shells of the M. trujiculus, and caldron-shaped holes in the rocks, may still be seen on the Phoenician shore; and on the coast of the Morea there is evidence that the M. brandaris was anciently used for the same purpose of collecting the purple secretion of which the dye was composed. The ancients bruised the smaller shells in mortars, but took out the animal from the larger ones. Several species of purpura also produce a fluid which gives a dull crimson dye.
An imitation of the purple dye prepared from uric acid, treated by nitric acid and combined with ammonia, was discovered by Prout in 1818, and afterward named by Liebig and Wöhler murexide. It is now produced from guano, and is used for the dyeing of foulard silks. The coloring fluid is secreted by a special gland situated on the mantle; in murex and purpura it is colorless when secreted, but on exposure to the sun becomes first yellowish, and finally violet, passing through the tints formed by the mixture of yellow, blue, and red. The M. tenuispina of the Moluccas is one of the handsomest species, 5 to 6 in. long. A handsome species is abundant on the Central American coasts.
Mures (Murex tenuispina).