an obsolete name of a submarine plant. It is also used for a kind of coral, or astroites, frequently found fossil in England.

ALCYONIUM Stagnum, in Ancient Geography, a lake in the territory of Corinth, whose depth was unfathomable, and in vain attempted to be discovered by Nero. Through this lake Bacchus is said to have descended to hell, to bring back Semele; (Pausanias.)