The Collaborative International Dictionary of English v.0.48:

Najas \Najas\ prop. n.
   The sole genus of the family Naiadaceae.

   Syn: Naias, genus Naias, genus Najas.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Najas
    n 1: sole genus of the family Naiadaceae [syn: Naias, genus
         Naias, Najas, genus Najas]