1885.] ME. F. E. BEDDARD ON THE CUCKOOS. 173 



are incomplete internally and closed by membrane ; in the first 

 fifteen rings the membranous area is very narrow, but it widens out 

 at the 16th ring, where the voice-organ is situated ; the 16th and 

 1 7th rings are considerably stouter and stronger than the rest, and 

 to the former are attached the syringeal muscles ; the extrinsic 

 muscles of the syrinx are given off from the trachea just before its 

 bifurcation. 



Gentropus rufipennis has a perfectly similar syrinx. 



Geococcyx affinis. — The syrinx of Geococcyx is constructed on 

 the same type as that of Pyrrhocetitor, and indeed resembles it so 

 closely that no special description is necessary ; the voice-organ is, 

 however, a little nearer to the trachea, the intrinsic muscles being 

 inserted upon the 13th bronchial semirings. 



Crotophaga ani is well known to possess a bronchial syrinx, which 

 may be considered as more specialized than that of Geococcyx and 

 Pyrrhocentor, in that the membrana tympaniformis is limited to the 

 posterior bronchial rings, commencing with about the 7th, and does not 

 extend up to the point of Infurcation of the bronchi ; in this respect 

 the syrinx of Crotophaga resembles that of Steatornis, which has 

 been carefully described by Prof. Garrod '. 



As in that bird, the bronchi arise from the trachea much as 

 they do in the Mammalia; the first nine rings of each bronchus are 

 entire ; the tenth and eleventh rings are considerably wider from side 

 to side, and their extremities are connected by membrane which 

 forms the inner neck of the bronchus ; the succeeding rings become 

 gradually narrower and are similarly completed internally by mem- 

 brane. In Steatornis the membrana tympaniformis is only of limited 

 extent, the posterior rings of the bronchi being, like the anterior rings, 

 complete ; in Crotophaga this is not the case — all the bronchial rings, 

 commencing with the seventh, are semirings ; there is a single pair 

 of slender intrinsic muscles attached one on each side to the tenth 

 bronchial semiring. 



Guira. — The syrinx of Guira pirigua is a very remarkable one ; 

 on a superficial view it appears to resemble very closely that of 

 Cuculus, and to be tracheo- bronchial instead of bronchial, as would 

 be expected from the close agreement in other structural characters 

 of Guira with Crotophaga and Geococcyx ; a closer examination, 

 however, shows that the syrinx is really bronchial. 



The apparent resemblance to the tracheo-bronchial syrinx is caused 

 by the fact that the voice-organ of Guira is situated at the upper 

 end of each bronchus close to the trachea, instead of being as in 

 Crotophaga nearer to the entrance of the bronchus into the lung ; 

 the first two or three rings of each bronchus are complete rings ; 

 from the fourth onwards the rings only occupy the outer section of 

 the bronchus and are completed internally by membrane ; the sixth 

 semiring is closely attached to the preceding bronchial rings and 

 upon it are inserted the syringeal muscles. There is another pecu- 

 liarity in this syrinx in the presence of an additional pair of muscles 

 lying on the dorsal surface and attached to the end of the trachea ; 



1 OoU. Papers, p. 188. 



