PASSERES. 



11 



of tlie essential features of this organ, in so far as they concern 

 the systematist, may be welcome. 



The syrinx is the term applied to the lower end of the wind- 

 pipe and the adjacent ends of the bronchi in birds, wherein these 

 portions have become variously modified to form the organ of 

 voice, which, in Mammals, is formed bv the larynx the upper 

 end of the windpipe. But while in the Mammals the larynx is a 

 comparatively stable structure, in the birds the syrinx presents a 

 very remarkable range of differences both in regard to its funda- 

 mental structural characters, as well as of musculature. 



For the present it must suffice to give a brief survey of the 

 essential features of the syrinx in the Passeres and, for systematic 

 purposes, the musculature is the dominant factor. 



The syrinx, then, in this Group presents wide contrasts, 

 even among Genera of the same Family, but nevertheless it 

 conforms in its essential characters with that of the Aves as a 

 whole. That is to say, it is formed of a number of bony or 

 cartilnginous rings and semi-rings some of which may be com- 

 pletely or partially welded held together by thin membranes 

 which serve not merely to support the framework, but also in the 

 production of the " voice." 



In the Anisomyodi the syringeal muscles are inserted either in 

 the middle or on to the dorsal or ventral ends of the semi-rings. 



Syrinx of Pitta angolensis (after Garrod, P. Z. S. 1876, pi. liii), showing the 

 Anisomyodian attachment of the intrinsic muscles at the middle of the bronchial 

 semi-rings. There is also a single pair of bronchial muscles, continued down 

 from the sides of the windpipe, insignificant in size, quite lateral, and termi- 

 nating by beir.g inserted into the middle of the outer surface of the second 

 bronchial semi-ring. 



In the Diacromyodi these muscles are 'inserted into both ends 

 of the semi-rings. They may be limited alwavs to one pair as 

 in Clamatores, to t\yo as in Oligomyodi and some Traclieoplionai 

 or there may be as many as seven pairs as in the Oscines. 

 But the structure of the syrinx itself, as apart from its 

 musculature, has been, and still is, a feature of importance in 



