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Show 300 MR. W. P. PYCRAFT ON THE [^Pr> 1^» tinguishable. With the Falconidse, however, the case is different; and it becomes a matter of nice discrimination to tell the coracoid of the Falcones, or Polybori, from that of one of the Striges. The Falcones may be distinguished by the absence of a supracoracoid foramen; but in the Polybori and Striges this foramen is present, and almost identical in size and position. The coracoid of the former can, indeed, scarcely be distinguished from that of the latter. In the Owls apparently the base of the coracoid is comparatively deeply grooved to fit the dorsal coracoid lip of the sternum ; whilst in the Polybori, what corresponds to the dorsal lip of the groove in the Owls is represented only by a low and incomplete ridge; lastly, in the Owls the linea aspera for the coraco-brachialis posterior generally lies near the extreme lateral border of the coracoid shaft; in the Polybori it lies nearer the middle line. The scapula does not afford much matter for comment of any systematic value. The acromial process in the Falconinse is pneumatic and very broad, so much so as to project considerably into the foramen triosseum, thereby considerably diminishing its size. The acromion may be produced conspicuously forwards, and this is particularly well seen in Neophron, where it constitutes the greater part of the inner wall of theforamen triosseum. The furcula in the Accipitres is remarkable for its great size and strength. It is U-shaped, with the limbs set wide apart, this latter feature being especially noticeable in the Buteonidse. In Serpentarius only does the furcula articulate with the carina (text-fig. 33, p. 297), as in the Storks. Furthermore, as we have already pointed out, Serpentarius agrees with the Storks in that the furcula does not develop a facet for- articulation with the coracoid. It bears a hypocleideum of considerable size, directed downwards, and presenting a keel-like border- for articulation with the carina. In the Cathartse only are the distal extremities pierced by a pneumatic foramen. This is very large and opens in the outer aspect of each limb, immediately behind the acrocoracoid. In the Falconidse the hypocleideum is vestigial or wanting. In Microhierax the furcula is not perceptibly bent upon itself, as in the larger members, nor are the limbs so wide apart. The length of the limbs of the furcula in Microhierax is relatively greater than in any other members of the order, since they equal the length of the carina sterni. In the Buteonidse the limbs of the furcula, as we have already remarked, are set widely apart, and are of great breadth at their distal ends; especially is this the case in such forms as Gypaetus, Haliaetus, and Aquila. The hypocleideum is vestigial or wanting. It appears to be largest in Aquila and Pandion. In some cases, Elanus for example, the proximal ends of the furcula are very slender, and in this particular the furcula resembles that of the Striges. The furcula of the Accipitres is more unlike that of the Striges than is the case with the sternum or coracoid, as |
