SYSTEMATIC POSITION OF THE PETRELS. 



to the fusion of the inner walls of the apposed paired tracheal rings, which, as they 

 approach the syrinx, become the separate branches just described. Superficially, 

 however, the fusion of these septate rings is so complete that they betray no evidence 

 of their true character, fused paired rings. 



The syrinx is supplied with but one pair of intrinsic muscles, which, according 

 to Forbes, are always attached to the fifth bronchial ring. But this interpretation 

 seems open to question. 



In some Albatroses, according to Swinhoe, the bronchi are convoluted as in 

 some Storks. 



The great size of the olfactory chamber in the Petrel, has been generally 

 overlooked ; but in this particular it is significant to note that they approach 

 the Gaihartidos. 



XXI 



