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Show 304 MR. W. P. PYCRAFT ON THE [Apr. 15, we meet with a type of pelvis found elsewhere only amongst the Striges. Its chief characteristic is the great deflection and shortening which the postacetabular ilium has undergone, and this is more marked in the Accipitrine innominate. The innominate bone of the Owls can, however, it would seem, be readily distinguished by the fact that the ischium is invariably produced backwards into a more or less slender spine resting on the pubis. In its general conformation the pelvic girdle of the Falconiformes, after the elimination of the Gypogeranidse and Cathartse, is very uniform : modifications from the type are very considerable. Some of the more noticeable, however, may profitably be commented upon here. The most conspicuous departure from the type is found in the pelvis of Pandion (text-fig. 37, p. 305), which is remarkably broad. This great breadth is due partly to the length of the outstanding transverse processes of the synsacrum, which support the roof of the anterior and posterior renal fossse; and partly to the exceptionally broad dorsal plane of the postacetabular ilium. The preacetabular ilium is sharply truncated anteriorly, and is widely separated from its fellow of the opposite side : so much so that a tubular aperture-the canalis ileo-lumbcdis- is left at the point where the mesial curved border leaves the synsacrum. The glenoid surface of the antitrochanter is oblong in shape and curved backwards. The ilio-ischiadic foramen is of great size. The obturator foramen is also very large, and closed posteriorly by the approximation of the pubis to the inferior border of the ischium, which, we may remark, turns abruptly upwards at its hinder end. The pubis is long, and develops a crescentic plate the cephalad segment of which fits closely to the upturned ischial border; beyond this it is con-tin ued backwards for a considerable distance as a rod-shaped bar nearly meeting its fellow of the opposite side. The pelvis of Pandion (text-fig. 37, p. 305) is an exaggeration of the typical Accipitrine pelvic girdle, which may be very well represented by such a form as is presented in Polyborus for example. Herein the pre- and postacetabular ilia are about equal in length. The former is a moderately broad concavo-convex plate directed outwards and downwards, meeting its fellow of the opposite side in the middle line, and having its superior border accentuated by a sharply-defined outstanding crest, which, in some forms, as in Haliaetus and Parabuteo for example, becomes still more strongly accentuated, forming an almost shelf-like projection. This border is continued backwards to terminate in an overhanging supra-trochanteric process. The postacetabular ilium expands into broad dorsal plates, terminating somewhat abruptly some distance from the end of the ischium, with which it is fused. In Accipiter and Elanus, and still more markedly in Polyboroides, the dorsal border of the ischium turns sharply inwards so that the dorsal plate of the ilium forms a relatively enormous ledge overhanging a deep cavern passing forwards into the obturator foramen. In |