The Collaborative International Dictionary of English v.0.48:

Scyllaea \Scyl*lae"a\, n. [NL. See Scylla.] (Zool.)
   A genus of oceanic nudibranchiate mollusks having the small
   branched gills situated on the upper side of four fleshy
   lateral lobes, and on the median caudal crest.
   [1913 Webster]

   Note: In color and form these mollusks closely imitate the
         fronds of sargassum and other floating seaweeds among
         which they live.
         [1913 Webster]