THE VOYAGE OF THE ' CHALLENGER.' 



407 



of syrinx (figs. 24, 25, p. 409), the two first bronchial rings being complete 

 anteriorly, the succeeding two being only semi-rings. The two last 

 tracheal are united with the two first bronchial behind, sending off a 



Fig. 20. 



Zool. Ohall. 

 Exp. vol. iv. 

 pt. xi. p. 39. 



Syrinx of Aeipetes antarcticus, from before. 

 Fig. 21. 



The same, from behind. The smaller figure represents a section of the trachea, to 

 show the imperfect septum dividing it. 



pessular process, which anteriorly, as usual, is continuous with the third Ibid. p. 38. 

 semi-rings. In younger birds (fig. 26, p. 409) the various rings concerned 

 remain more distinct, the pessular bar, it is pretty clear, being largely 

 formed by the third semi-rings anteriorly, their backward prolongation Ibid. p. 39. 

 fusing behind with cartilaginous elements developed in connection with 



