It is the adrectal gland, and in the genera Murex and Purpura secretes a colourless liquid which turns purple upon exposure to the atmosphere, and was used by the ancients as a dye.
The gland has been found in both sub-orders of the Pectinibranchia, in Cyclostoma and Cypraea among the Taenioglossa, in Hemifusus, Cassis, Nassa, Murex, Fasciolariidae, Turbinellidae, Olividae, Marginellidae and Conidae among the Stenoglossa.
Fusus, Pyrula, Purpura, Murex, Nassa, Trophon, Voluta, &c. The float of the pelagic Janthina, to which the egg-capsules are attached, probably is also formed by the secretion of the pedal gland.
It is famous for its purple-yielding murex, pearls and mother-of-pearl.
With regard to natural products the country has few worth mentioning; minerals are found in the Lebanon, but not in any quantity; traces of amber-digging have been discovered on the coast; and the purple shell (murex trunculus and brandaris) is still plentiful.
One of their objects was the collection of murex, of which an enormous supply was needed for the dyeing industry; specially famous was the purple of the Laconian waters, the isles of Elishah of Ezek.
Murex purple and imitations of murex dye.
This was properly the name of the shellfish (Purpura, Murex) which yielded the famous Tyrian dye, the particular mark of the dress of emperors, kings, chief magistrates and other dignitaries, whence "the purple" still signifies the rank of emperors or kings.
Oysters do not flourish in water containing less than 3% salt; and hence they are absent from the Baltic. The chief enemies of oysters are the dog-whelk, Purpura lapillus, and the whelk-tingle, Murex erinaceus, which bore through the shells.