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Show 18/3.] ANATOMY OF STEATORNIS. 529 the acetabula, there is a weak feathering which blends with the lumbar tracts. These last are consequently not very distinctly defined, and consist mainly of weakly feathered tracts, running from the knee obliquely downwards and backwards, leaving the tibiae almost bear, with the exception of a few semiplumes which are scattered below the front of the knee. Between the rami of the jaws the large triangular surface is naked at the sides and weakly feathered along the middle line up to the symphysis (as in the Owls), where there are a few vibrissae, directed forwards. From this submaxillary feathered portion the inferior neck-tract springs ; and behind the angle of the jaw a weak branch is sent up, on each side, to join the dorsal tract and head-covering behind the ears. A little lower down the inferior tract becomes more defined, though not strong ; it continues simple as it descends, being of the same breadth as the lateral neck-spaces. Just above the upper or scapular extremities of the furcula it ceases in the middle line, leaving a bare interclavicular space; but it develops a branch on either side, which expands over the chest to form the pectoral tracts. The pectoral tract of each side is double, the inner of its divisions being the continuation of the main tract, which descends, narrow and strong, close to the carina sterni in its upper part, but further separated below, leaving over the epigastric region of the abdomen a considerable median space, which lower down is again reduced by their convergence to the anus, just in front of which they terminate. Each outer pectoral branch of the inferior tract is weak and very diffused, covering the sides of the body, leaving a narrow space between it and the main stem, except at the points just in front of the scapular ends of the furcula, from which they spring, and below the inferior margin of the sternum, where they again blend, and continue down side by side, after their contact, nearly to the anus, the outer branch being the weaker and less defined. There is a weak hypopteral tract continued from the outer margin of the external pectoral branch. The under wing-surface is feathered along the forearm in several rows. The margin of the patagium is thickly set with short strong plumes. The humeral tract is strong and separated by a narrow space from the well-covered upper wing-surface. There is no aftershaft to the feathers. There are ten primary remiges, and twelve secondary, of which the ten distal resemble each other, and the two at the elbow are reduced in size. The upper wing-coverts do not extend more than or quite so m u c h as halfway down the secondary remiges. There are ten rectrices. The above described pterylosis clearly indicates that in the arrangement of its feathers Steatornis more closely resembles the Strigidae than the Caprimulgidse, though it differs considerably from both. It resembles the Strigidae and differs from the Caprimulgidae in having no aftershaft to the contour feathers, in not having the occipital tract divided up into narrow longitudinal rows, in having spaces on each side of the submaxillary tract, in having PROC. ZOOL. Soc-1873, No. XXXIV. 34 |