BUCEROTE8 



very 



slender syringeal muscles are attached to the anterior margin 

 of the last tracheal ring. 



The peculiar-shaped tracheal rings are hardly recognis- 

 able until about the fourteenth from the end. 



Buceros rhinoceros has a syrinx which is not 

 different from that of 

 Acer os. The same rings 

 are fused to form an os- 

 sified box ; but the fusion 

 between the several rings 

 is hardly so extensive as 

 in Acer os ; furthermore 

 the syringeal muscles are 

 attached to the posterior 

 border of the last tracheal 



ring. 



In Sphagolobus atra- 



tus there is very little 

 fusion between any of 

 the last tracheal rings ; 

 the last three rings, which alone show any signs of ossification, 

 are fused for a very short space anteriorly ; posteriorly there 

 is no fusion at all, and the pessulus can be plainly seen to be 

 connected with the antepenultimate ring. Although the last 

 tracheal rings are not fused, they are very closely applied 

 together, and no membranous interspaces are left. 



Ceratogymna elata, which is, like the last, a compara- 

 tively small species, has a very similar syrinx ; indeed, I can 

 find no differences sufficiently tangible to be described. 



Buceros lunatus and B. bicornis, which are both large 

 species, hardly present any differences from B. rhinoceros. 



Bycanistes subcylindricus has a syrinx which, although 

 of about the same size as that of Ceratogymna elata, shows 

 certain differences which are worth putting on record. In 

 the first place, the syrinx is much compressed from side to 

 side at the level of the last tracheal ring; in the second 

 place, the last tracheal ring is very much more arched than 

 usual ; it forms, indeed, almost a complete semicircle. The 



FIG. 103. SYRINX OF Bitcorvus abyssini- 

 ciis. FKONT VIEW. (AFTER BEDDARD.) 



