(Science: marine biology) Any gastropod of the genus ianthina, of which various species are found living in mid ocean; called also purple shell, and violet snail.
It floats at the surface by means of a raft, which it constructs by forming and uniting together air bubbles of hardened mucus. The Tyrian purple of the ancients was obtained in part from mollusks of this genus.
alternative forms: janthina.
Origin: NL, fr. L. Ianthinus violet-blue, gr.; violet _ flower.