Source : Webster's Revised Unabridged Dictionary (1913)

Anas \A"nas\, n. [L., duck.] (Zo["o]l.)
   A genus of water fowls, of the order Anseres, including
   certain species of fresh-water ducks.

Source : WordNet®

Anas
     n : type genus of the Anatidae: freshwater ducks [syn: {genus
         Anas}]