402 



ON THE PETRELS COLLECTED DURING 



Zool. CbalJ. 

 Exp. vol. iv. 

 pt, xi. p. 35. 



In Fulmarus glacialis the syrinx is very similar ; the four bronchial 

 rings are anteriorly ossified, as are many of the tracheal rings in their 

 median area. The tracheal septum is still more developed than in 

 Thalassoeca, extending for about the lower two fifths of the trachea a 

 distance of nearly 2| inches. 



Fig. 11. 



Syrinx of Prion vittatus, from before, 

 Fig, 12. 



The same, from behind. 



Ibid. p. 36. The extraordinary syrinx of Ossifraga is a still further modification of 



this tyre (figs. 17, 18^19, pp. 405, 406). Anumber of the last tracheal rings 

 (nine on one side, ten on the other, in the specimen a young one figured) 

 become completely ossified, as are the first four or five bronchial rings, 

 of which only the first two are complete. The inferior part of the 

 trachea is divided inferiorly for a short way into two quite complete and 

 separate tubes ; the posterior ends of the lowest tracheal rings being so 

 much incurved that each actually, inferiorly, forms two complete rings, 



