Source : Webster's Revised Unabridged Dictionary (1913)

Attagas \At"ta*gas\, Attagen \At"ta*gen\, n. [L. attagen a kind
   of bird, Gr. ?, ?.] (Zo["o]l.)
   A species of sand grouse ({Syrrghaptes Pallasii}) found in
   Asia and rarely in southern Europe.