1880.] TRACHEA AND SYRINX IN CERTAIN BIRDS. 323 



In the Ardeidse, on the other hand (including the Herons, Bitterns, 

 and Scopus, which to this extent is a Heron'), the syrinx has what 

 may perhaps be called a more typical form. The hronciii are short, 

 and the rings which compose them are only halt-rings, and are com- 

 pleted on the inner side by membrane ; there is a pair of intrinsic 

 muscles arising beneath the sterno-tracheal muscles and inserted 

 onto the first bronchial semiring ; the bronchidesmus only commences 

 at about the level of the fourth or fifth bronchial semiring ; anteriorly, 

 therefore, there is a free communication between the upper and lower 

 surface of the bronchi : the first two bronchial rings are more or less 

 ossified and closely connected with each other and with the preceding 

 tracheal rings ; the latter undergo no modifications such as those 

 which exist in the Storks, but are of uniform thickness, closely 



F\or. 2. 



Syrinx of Ahdlmia sphcnorhyncha. 



applied and often ossified. Tlie foregoing account does not of course 

 pretend to he a detailed description of the syrinx in the two families, 

 init it is sufficient to indicate tlie main differences and to serve as a 

 basis for comparison of them with the syrinx of Xenorhi/nc/ttts sene- 

 ffalensis and of Abdimia sphenorhyncha, which are in some respects 

 intermediate between the two types. 



In Xenorhynchus there is a transition to the Ardeine syrinx in 

 that the upper rings of both bronchi are incomplete and are (tig. 3) 

 closed by membrane on the inner side. 



It appears therefore that the syrinx of Xenorhynchus agrees with 

 that of other Storks in the peculiar arrangement of the lowermost 



' See F. E. Beddard, " A Contribution to the Anatomy of Scoims umbretfa," 

 P. Z.S. 1884, p. 543. 



