The Collaborative International Dictionary of English v.0.48:

Plumularia \Plu`mu*la"ri*a\, n.; pl. L. Plumularl[ae], E.
   Plumularias. [NL.] (Zool.)
   Any hydroid belonging to Plumularia and other genera of the
   family Plumularid[ae]. They generally grow in plumelike
   forms.
   [1913 Webster]