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Show 1889-] ANATOMY OF PICARIAN BIRDS. 593 Bucorvus possesses a femoral caudal muscle, which was stated by Garrod to be absent1, but is described and figured by Gadow 2. 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 Caprimulgidae ; 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 Caprimulgidae, 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 Podargus 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 monograph3 of the Family, allows no less than 19 distinct genera ; Dubois 4 considers that there are only four genera of Hornbills, while G. R. Gray 5 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 Bucerotidae 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 6, the structure of the syrinx (see p. 588), and the presence of a tendinous " 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. 2 Loc. cit. 3 A Monograph of tbe Bucerotidas. London, 1877-82. 4 " Eevue critique des Oiseaux de la Famille des Bucerotides," Ball. Mus. d'Hist. nat. de Belgique, t. iii. (1884-5), p. 187. 5 Hand-list, p. 127. . . 6 " O n a peculiarity in the Carotid Arteries, and other points in the Anatomy of the Ground Hornbill (Bucorvus abyssinicus)," P. Z. S. 1876, p. 60, and Coll. Papers p 316 W . Ottley, " A Description of the Vessels of tbe Neck and Head in the Ground Hornbill," P. Z. S. 1879, p. 461. |
