The Collaborative International Dictionary of English v.0.48:

Crossopterygii \Cros*sop`te*ryg"i*i\ (kr?s-s?p`t?-r?j?-?), n.
   pl. [NL., fr. Gr. ??? tassels, a fringe + ?????, dim. of ????
   wing, fin.] (Zool.)
   An order of ganoid fishes including among living species the
   bichir (Polypterus). See Brachioganoidei.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Crossopterygii
    n 1: fishes having paired fins resembling limbs and regarded as
         ancestral to amphibians [syn: Crossopterygii, subclass
         Crossopterygii]