ON THE TRACHEA IN THE " RATITE " BIRDS. 235 



Fig. 3. 



Bifurcating trachea of Apteryx mantelli, from before. 

 Fig. 4. 



\ 



The same, from behind. About twice the natural size. 



succeeding bronchial semirings are perfectly simple, rather deep and stout 

 pieces of cartilage, separated by narrow interannular spaces, and com- 

 pleted internally by a broad membrana tympaniformis ; nowhere do they 

 become complete circles. As in Struthio, there is no pessulus, and no 

 intrinsic muscle. There is a slight antero-posteriorly directed vertical 

 fold of mucous membrane between the two bronchial apertures internally, 

 and also a feebly developed vocal cord on the external wall of the bronchi, 

 where they diverge from the trachea. The lateral muscles stop some 

 way before the end of the trachea, at the place where the sterno-tracheales 

 are inserted. Apteryx australis, A. haasti, and A. oweni have all been 

 examined by me, and all agree closely in their tracheal structure with 

 A. mantelli. My specimens of A. australis and A. oweni (two) agree 

 together in having the last three tracheal rings incomplete posteriorly ; 

 whilst in A. mantelli and A. Jiaasti, of which I have seen only single 

 specimens, the last ring alone is complete. 



In the Casuariidse we meet with peculiarities in the structure of the 



P.Z.S. 1881 



p. 782. 



