1889. | ANATOMY OF PICARIAN BIRDS, 593 
Bucorvus possesses a femoral caudal muscle, which was stated 
by Garrod to be absent’, but is described and figured by Gadow °. 
In Aceros the head of the anconeus is single; it is double in 
Bucorvus and 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 which 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- 
mulgide ; 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 
Caprimulgide, these birds probably, in spite of the resemblauce 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 Bucerotide 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 
Bucerotide. With regard to the other Horubills 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 
I Loe. ct. 2 sloei cit. 
3 A Monograph of the Bucerotide. London, 1877-82. 
4 “Revue critique des Oiseaux de la Famille des Bucerotides,” Bull. Mus. 
d’Hist. nat. de Belgique, t. iii. (1884-5), p. 187. 
® Hand-list, p. 127. 
* “On a peculiarity in the Carotid Arteries, and other points in the Anatomy 
of the Ground Hornbill (Bucorvus abyssinicus),” P. Z. 8. 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, 8. 1879, p. 461. 
