1889.] ANATOMY OF PICARIAN BIRDS. 593 



Bucorvus possesses a femoral caudal muscle, which was stated 

 bv Garrod to be absent^, but is described and figured by Gadow ". 



In Aceros the head of the anconeus is single ; it is double iu 

 Bucorvus aud Buceros. 



I do not attempt in the present paper to discuss in detail the 

 affinities of the Hornbills to other Picarian birds, as material hardly 

 exists at present for comparison. The only birds to wliich they 

 might be supposed to be allied, and to which they show a particular 

 resemblance in any well-marked character, are the Colies and Capri- 

 mulgidae ; the presence of the ligament uniting the biceps to the 

 tensor patagii in Bucorvus is no doubt the representative of the 

 muscular slip existing in the former groups. With regard to the 

 Caprimulgidse, these birds probably, in spite of the resemblance noted 

 above, would not be regarded by many ornithologists as coming 

 anywhere near the Hornbills. I may remark, however, that Po- 

 dargus has the same great development of muscular fibres in the 

 horizontal septum attached to the gizzard that has been recorded 

 above in the Hornbills. 



The main object of this paper is to endeavour to fix some of the 

 generic types, about the limits of which the most diverse opinions 

 have been held. 



To mention a few of these:- — Elliot, in his illustrated monograph^ of 

 the Family, allows no less than 19 distinct genera ; Dubois * considers 

 that there are only four genera of Hornbills, while G. R. Gray ° only 

 admits two, Bucorvus and Buceros. 



There can be no doubt whatever that Bucorvus forms a very 

 distinct type of Hornbills, even in its habits. Although it does 

 not differ from the other Bucerotidse in the absence of the femoro- 

 caudal muscle as Garrod believed it did, Bucorvus exhibits a larger 

 number of structural differences from other forms than any of 

 these do from each other. The peculiarities of the carotid arteries ^ 

 the structure of the syrinx (see p. 588), and the presence of a ten- 

 dinous " biceps slip " mark out Bucorvus as far removed from other 

 Bucerotidae. With regard to the other Hornbills it is not so easy 

 to mark out a number of distinct genera. 



The form of the syrinx in Bycanistes is peculiar, and, as far as 

 my observations go, restricted to this genus ; but unfortunately I 

 am not in a position to add any other differential characters. It 

 will be remembered, however, that the species which constitute the 

 genus Bycanistes are African and do not extend into the Oriental 

 Region ; there is thus some further support given to the view that 



1 Loc. cit. ^ Loc. cit. 



3 A Monograph of the Bucerotidis. London, 1877-82. 



* " Eevue critique des Oiseaux de la Famille des Bucerotides," Bull. Mus. 

 d'Hist. nat. de Belgique, t. iii. (1884-5), p. 187. 



5 Hand-list, p. 127. 



" " On a peculiarity in the Carotid Arteries, and other points in the Anatomy 

 of the Ground Hornbill {Bucorvus abi/ssinicus)," P. Z. S. 1876, p. 60, and Coll. 

 Papers p 316. W. Ottley, " A Description of the Vessels of the Neck and 

 Head in the Ground Hornbill," P. Z. S. 1879, p. 461. 



