Source : Webster's Revised Unabridged Dictionary (1913)

Astacus \As"ta*cus\, n. [L. astacus a crab, Gr. ?.] (Zo["o]l.)
   A genus of crustaceans, containing the crawfish of
   fresh-water lobster of Europe, and allied species of western
   North America. See {Crawfish}.

Source : WordNet®

Astacus
     n : type genus of the family Astacidae; Old World crayfish [syn:
          {genus Astacus}]