296 STRUCTURE AND CLASSIFICATION OF BIRDS 



referred to the cleido-tracheal extrinsic pair (see below), A 

 very singular syrinx is that of the male Tetrao tetrix (fig. 147). 

 On each side of the trachea at the lower end is an ' immense 

 irregular tumefaction, connected with its fellow by a bridge 

 of fatty tissue.' It appears to be mucous in its chemical 

 nature ; but it may possibly have some relation to the tracheal 



Pig. 147.- 



■ Syhinx op Male Tetrao tetrix. 

 (Afteb Gaeeob.) 



Pboni View. 



box of the male ducks, and be thus another of those many 

 unexpected resemblances between the two groups. 



The Cracidee (fig. 148) generally possess the intrinsic mus- 

 cles, which are, however, short, as in the other Galli. The 

 syrinx itself has no salient characters by which it may be 

 distinguished from the Alectoropodes. 



Gaeeod ' has also described and figured (fig. 150) the 

 syrinx of the megapode Megacephalon maleo. It is rather 



' ' On the Anatomy of the Maleo,' P. Z. S. 1878, p. 629. 



