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Show 152 MIL w. P. PYCRAFT O N T H E OSTEOLOGY [Feb. 20, enable me to say much concerning the form of the pelvis in these somewhat heterogeneous groups, but those genera which I have so far examined in this connection show considerable specialisation in adaption to climbing habits. In the smaller Synallaxine species the pelvis resembles that of the Philepittida?, having the ischia widely expanded posteriorly and produced into a long rod-like foot bent sharply on its long axis, but the pre-acetabular ilium is relatively shorter. In Siptornis the pre-acetabular ilia are widely separated, being divided by a deep trough on either side of the synsacral crest; but in Synallaxis and Homorus, by the shortening of the transverse process of the supporting vertebra?, the innominate bones almost touch one another above the synsacral Crest. In Pseudoeolaptes the pre-acetabular ilia are subcorneal in shape and rise to the level of the synsacral crest, but are separated therefrom by a narrow space. The form of the ischium agrees very closely with that which obtains among the more specialised Dendrocolaptines : since it turns downwards instead of running backwards beyond the level of the post-acetabular ilium ; by this means the depth of the hinder region of the pelvis is greatly increased. In Xiphorhynchus and Dendrocolaptes this deepening is especially noticeable ; furthermore, this is associated with a tendency to close up the obturator fissure by the ossification of the tendinous fascia stretched between the inferior border of the ischium and the pubis. In Xiphorhynchus this newly ossified matter hangs down from the ischium in the form of a delicate curtain of bone and is continued forwards and downwards to form a broad bony plate enclosing the obturator foramen. The pelvis of Batara, one of the Formicariida?, presents some extremely interesting features. In many respects resembling the pelvis of Dendrocolaptes, it differs therefrom in having the dorsal border of the pre-acetabular ilium strongly arched, and this curve is followed by the synsacral crest which lies between. The ischium, in its general shape and characters, also closely resembles that of Dendrocolaptes, but it differs therefrom mainly in that it fuses completely with the pubis, which is unusually broad and also very short. In all these pelves the fovea lumbalis is extremely small, and the fovea ischiadica and pudendalis are confluent. vii. THE PECTORAL LIMB. The pectoral limb in the groups here described presents a somewhat remarkable uniformity even in structural details : so much so that it would be difficult, on the evidence of the wing alone, to determine to which of these families the skeleton belonged. With but few exceptions the forearm is the longest segment of the wing, but then is never markedly longer ; the arm and manus are subequal. There is no coraco-humeral groove, and the characteristic pit for the braehiaUs anticus is situated below and proximad of the ulnar condyle. |