The Collaborative International Dictionary of English v.0.48:

Polygordius \Pol`y*gor"di*us\, n. [NL. See Poly-, and
   Gordius.] (Zool.)
   A genus of marine annelids, believed to be an ancient or
   ancestral type. It is remarkable for its simplicity of
   structure and want of parapodia. It is the type of the order
   Archiannelida, or Gymnotoma. See Loeven's larva.
   [1913 Webster]