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Show 1885.] MR. 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 17th 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. Centropus rufipennis has a perfectly similar syrinx. Geococcyx affinis.-The syrinx of Geococcyx is constructed on the same type as that of Pyrrhocentor, 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 bifurcation of the bronchi; in this respect the syrinx of Crotophaga resembles that of Steatornis, which has been carefully described by Prof. Garrod 1. 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 membrane. 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 peculiarity 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 Coll. Papers, p. 188. |