The Collaborative International Dictionary of English v.0.48:

Tracheophonae \Tra`che*oph"o*nae\, n. pl. [NL., from trachea +
   Gr. fonei^n to sound.] (Zool.)
   A group of passerine birds having the syrinx at the lower end
   of the trachea.
   [1913 Webster]