Lanthina, a genus of gregarious, pelagic gasteropods, in the same division as the river snail (Paludina), Trochus, Turbo, &c. The shell is snail-like, but delicate, translucent, and blue in colour. In the warmer seas the animal floats by expanding its 'foot' on the surface, and is drifted about by currents, occasionally on to British shores.
Shell, animal, and raft.
It is most remarkable for an airy raft which it secretes, and eventually sets adrift, laden with egg-capsules, like those of the whelk. The animals exude a violet secretion, and seem to feed on Veletta and other Cœlenterates of the Portuguese man-of-war type.