1880.] MR. W. A. FORBES ON LEPTOSOMA DISCOLOR. 473 



be done in birds. As far as I can make out, they do not, however, 

 fuse, but are continued up to the head and there diverge. In Opis- 

 thocomus^ Prof. Garrod found a somewhat similar condition, though 

 he says nothing about the vessels being minute. In Leptosoma they 

 have the appearance of white fibrous cords, and they may possibly 

 be, like the carotids of Bucorvus^, no longer functional as blood- 

 channels. But satisfactorily to decide this, as well as the ultimate 

 termination of these carotids, fresh or injected specimens will be 

 necessary. 



In both the Cuculidse and Coraciidse there are two equisized 

 carotids, which are as free as usual. 



As regards the vocal organs, there are present but one pair of 

 extrinsic muscles, which diverge to be attached to the "costal 

 processes " of the sternum. The syrinx possesses a single pair of 



Fig. 4. Fig. 5. 



Fig. 4. The syrinx of LeTpfosoma seen from in front, the museles of the left 



side having been removed. 

 Fig. 5. The same, from behind. (Both are twice the natural size.) 



intrinsic muscles, as usual. This organ having been previously un- 

 known in Leptosoma, I here take the opportunity of describing 

 and figuring it. 



The tracheal rings, which, as nsual, interlock with each other for 

 the greater length of the trachea, are well ossified, and only separated 

 by narrow intervals. They gradually narrow as they approach the 

 thorax, the last two being the narrowest of all. The penultimate 

 tracheal ring is produced downwards in a triangular way behind, as 

 is the terminal one in front ; behind, this last ring bears the ante- 

 riorly-directed narrow pessulus, which intervenes behind between 

 the inturned ends of the first pair of bronchial semirings, but in front 

 does not appear, stopping short before it reaches the anterior surface 

 of the bifurcating trachea. 



Like the tracheal rings, the first three bronchial semirings are 

 well ossified, and separated from each other only by very narrow 

 interannular intervals. They are nearly straight, with only a very 

 slight concavity upwards, and increase in depth as they descend. In 

 front the semirings of opposite sides are separated from each other by 



1 P. Z. S. 1879, p. 112. 



= Vide Mr. Ottley's paper on this bird, P. Z. S. 1879, pp. 461-467. 



