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.
- Female of Purpura lapillus removed from its shell; the mantleskirt cut along its left line of attachment and thrown over to the right side of the animal so as to expose the organs on its inner face.
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.
Paludina, Purpura, Nassa, Vermetus, Neritina.
In the veliger stage many Pectinibranchia (Purpura, Nassa, &c.) exhibit, in the dorsal region behind the head, a contractile area of the body-wall.
In some cases all the eggs in a capsule develop; in other cases one egg only in a capsule (Neritina), or a small proportion (Purpura, Buccinum), advance in development; the rest are arrested either after the first process of cell-division (cleavage) or before that process.
" Anomia " (1854), " Mytilus " (1856), " Dentalium " (1856-1857), " Purpura " (1859), " Haliotis (1859), " Vermetus " (1860).
Formerly it was used, as the origin of the name shows, of the deep crimson colour called in Latin Purpura, purpureus and in Greek 7rop41upa, irop4 peos (from 7ropcupecv, to grow dark, especially used of the sea).
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.