330 Mr. Yarkell on the Organs of Voice in Birds. 



Fig. 9. Front view of the same trachea, a. Part of the tube. 

 b. The triangular bone between the crescent-shaped 

 bones. 

 9. Side view of the trachea of the Raven {Corvus Corax). 



a. Part of the tube. b. Point of divarication, c. Bron- 

 chia outside. 



10. Another view of the same, one bronchia being removed 



to show the inner portion (membrana tympaniformis) 

 of the other, letter c. 



11. Bone of divarication in the Raven (Corvus Corax), seen 



from below, a*. Posterior part, a, a. Cross-bone. 



b, h. The sides. 



12. Lower part of the trachea of the Great Black-backed 



Gull [Larus marinus). h. The triangular bone of di- 

 varication ; and c, a. The triangular cross-bone. 



Tab. XVIII. 



Fig. 1 & 2. Front and side views of a trachea having one pair of 

 muscles of voice, a, b, & c. Refer as before, d, d. The 

 first pair of muscles. 



3. Side view of a trachea with two pair of muscles of voice. 

 d. Sterno-tracheal or first pair. e. The second pair. 



4 & 5. Front and side views of part of the trachea of the Gan- 

 net (Pelicanus bassanus), having two pair of muscles of 

 voice. d,d. The first pair, sterno-tracheal. e,e. The 

 second pair. 



6 & 7. Front and side views of part of the trachea of the 

 Great Blue and Yellow Macaw {Psittacus Ararauna), 

 having three pair of muscles of voice, d, d. The first 

 pair. e,e. The second pair. f,f. The third pair. 



8. Side view of the same, the muscles partly detached for 



distinction. Letters of reference the same. 



Fig. 



