hydrophyllium

Hydrophyllium \Hy`dro*phyl"li*um\, n.; pl. L. Hydrophyllia, E. Hydrophylliums. [NL., fr. Gr. "y`dwr water + ? a leaf.] (Zool.) One of the flat, leaflike, protective zooids, covering other zooids of certain Siphonophora. [1913 Webster]