ianthina

Webster's Dictionary (1913)

Origin: NL., fr. L. ianthinus violet-blue, Gr. …; … violet + … flower.

Zoology Any gastropod of the genus Ianthina, of which various species are found living in mid ocean; — called also purple shell, and violet snail. [Written also janthina.]

☞ 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.

Webster’s Revised Unabridged Dictionary (1913), from GCIDE 0.54