464 STRUCTURE AND CLASSIFICATION OF BIRDS 



also figured a good many of the syringes of the ducks in 

 illustration of this matter. The only ducks in which there is 

 certainly no modification of the syrinx of this kind are 

 Biziiira lobata, (Edemia nigra, and Melanitta fusca ; in the 

 former bird FORBES l has described a plain syrinx (fig. '2'Jo) 

 with a box at the bifurcation of the bronchi formed of the 

 last tracheal and of a few of the anterior bronchial semi-rings. 



He suspects, however, that the 

 genus Erismatura 2 will be found 

 to have a similar syrinx minus a 

 lateral outgrowth, as MAcGiLLi- 

 VEAY appears to have described 

 something of the kind. Somateria 

 molUssima has a very slight sym- 

 metrical enlargement of the syrinx. 

 A very marked characteristic of the 

 Anseres is the possession of two 

 FIG. 223.-SYRIXX OF Biziura $ g of extr i ns i c tracheal muscles. 



(AFTER FORBES). 



In this they agree with Pala- 



medeidas. The single pair of intrinsic muscles are as a rule 

 attached to the third or fourth tracheal ring in front of 

 the syrinx in the ducks. 



Among the Cijgnince (swans) there is frequently a looped 

 trachea, the coils being intrasternal. This is so with both 

 sexes of C. ferns, C. buccinator, C. americanus, and C, 

 Bewicki ; there appears to be a trace of the looping in C. 

 atratus. In C. olor, C. immutabilis, C. nigricollis, and C. 

 coscoroba the windpipe is straight in both sexes. It is 

 interesting to note that in C. buccinator, at any rate, the 

 intrinsic muscles do not follow the coils that bridge across 

 the loop. This species of swan is also remarkable for the 

 extraordinary dilatation of the middle of each bronchus, which 

 is, again, characteristic of both sexes. These dilatations would 



O 



be almost spherical were it not for the irregular crumpling 



1 'A Note on some Points in the Anatomy of an Australian Duck (Biziitrn 

 lobata),' P. Z. S. 1882, p. 455. 



2 ' There is no expansion or tympanum, as in other ducks ' (Orn. Bioyr. iv. 

 1838, p. 331). 



