ON LEPTOSOMA DISCOLOR. 157 



of the fourth digit in Leptosoma, shows that there are no real grounds for 

 calling Leptosoma a " zygodactyle " bird *. 



As regards other points, it may be mentioned that the vessels and 

 nerves of the thigh are normal; that is to say, the sciatic nerve and 

 artery and. the femoral vein are all present in their normal position. 



There are two carotid arteries present, both of them being unusually 

 small, the left particularly so. They run up in the usual converging 

 way, springing from the vertebral arteries into the hypapophysial canal 

 of the neck, and there become so closely applied to each other that it is 

 impossible to dissect them away as can usually be done in birds. As far P. Z. S. 1880, 

 as I can make out, they do not, however, fuse, but are continued up to p * 

 the head and there diverge. In OpistJiocomus t 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 J, 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 CuculidaB and CoraciidsD 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 intrinsic muscles, as 



Fig. 4. Fig. 5. 



Fig. 4. The syrinx of Leptosoma seen from in front, the muscles of the left side having 



been removed. 

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



usual. This organ having been previously unknown in Leptosoma, I 

 here take the opportunity of describing and figuring it. 



The tracheal rings, which, as usual, interlock with each other for the 



* In Podargus cuvieri, where the outer toe is reversed in perching, and in Coitus, 

 where the toes are directed at various times in very different ways, the "same blended" 

 distribution of the deep plantar tendons obtains. 



t P.Z.8. 1879, p.112. 



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



