1881.] 



TRACHEA IN THE RATITE BIRDS. 



Fi-. 3. 



■781 



Bifurcating trachea of Apferyx mantelli, from before. 

 Fig. 4. 



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



plete in the middle line behind ; it is slightly wider and stronger 

 than the preceding rings. The first two bronchial semirings on 

 each side closely resemble it in form ; the first semirings of opposite 

 sides are almost in contact at both extremities, the next pair being 

 more widely separated at those joints. There is only a narrow space 

 between the last tracheal and the first bronchial ring. The suc- 

 ceeding bronchial semirings are perfectly simple, rather deep and" 

 stout pieces of cartilage, separated by narrow interannular spaces, 

 and comjileted internally by a broad membrana tympanifoniis ; no- 

 where do they become complete circles. As in Struthio, there is no 

 pessulus, and no intrinsic muscle. There is a slight antero-pos- 

 teriorly 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 sternotracheales are 

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



