Contributions to Bird-Anatomy and Classification. 7 



To these four conditions, duly noticed in Prof. Garrod's 

 paper above quoted, may be added two more : — 



(5) When the right carotid only is present, as is the case*, 

 as discovered by him, in the Bustards of the genus Eupo- 

 dotis. 



(6) In Bucorvus abyssinicus, as discovered by my friend 

 Mr. W. Ottley, who, at Prof. Garrod's request, undertook a 

 reexamination of the question, the two carotid arteries are 

 reduced to fibrous imperforate cords, and their place is taken 

 (functionally) by two vessels which are apparently enor- 

 mously enlarged equivalents of the comes nervi vagi of other 

 birds f. 



From these facts it is evident that, taken per se, the dispo- 

 sition of the carotid arteries has not much significance amongst 

 birds, there being many families in which, whilst the majority 

 of the species have two, some have only one carotid. This, 

 for instance, is the case with Toccus and Buceros amongst 

 the Bucerotidse, P/o^2<s and Phalacrocorax amongst the Stega- 

 nopodes, Cypselus and Cypseloides in the Swifts, &c. : in all 

 these cases the first-named genera have but one, the others 

 two, carotids. In other cases, however, the characters of 

 the carotids hold good through very large groups : thus no 

 Passerine bird has ever yet been found with more than a left 

 carotid, and no Pigeon, Duck, or Bird of Prey without two 

 normally placed ones. 



III. The Disposition of the Vessels of the Thigh. 



In Man and other Mammals, so far as I am aware, the main 

 nerve of the leg is the sciatic ; the main artery and vein are 

 the femoral, running in the front of the leg. In birds, as a 

 rule, the main artery accompanies the sciatic nerve, running 

 close above and parallel to it ; the vein remains the femoral. 



To these rules certain exceptions were first pointed out by 



* P. Z. S. 1874, p. 473. 



t '' On a Peculiarity in the Carotid Ai'teries and other Points in 

 the Anatomy of the Ground-Hornbill," P. Z. S. 1876, pp. 60, 61. Also 

 "A Description of the Vessels of the Neck and Head in the Ground- 

 Hornbill (Bucorvus abyssinicus), by W. Ottley, F.E.C.S.," P. Z. S. 1879, 

 pp. 461-467. 



