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Show 905 DR. R. W. SHUFELDT ON THE OSTEOLOGY OF THE [Dec. 1, with the greatest velocity beneath the water, the Swift in its flight paddles the air with an equal rapidity of wing, both birds requiring powerful longi colli (and consequent firm and extensive supports for them), these muscles being the ones brought into action in seizing their prey during the height of this volant motion. The fifteenth, sixteenth, seventeenth, eighteenth, and nineteenth vertebrae are true dorsals, having perfect ribs connecting them with the sternum ; and they have low neural spines which interlock with each other at their ends, these vertebras all being freely movable upon one another. Nothing of special importance characterizes these ribs ; all have strong epipleural appendages anchylosed to them, save tbe last pair, in which they are absent. Two pairs of feeble ribs also spring from beneath the sacrum, the hinder pair being very rudimentary in some specimens. From the twentieth to the twenty-ninth vertebrae, all inclusive, are firmly anchylosed together to form the pelvic sacrum. To their outer common diapophysial margins, the ilia make thorough connection, the sutural traces being nearly absorbed. A few small foramina are found upon the dorsal aspect among the fairly defined transverse processes. Six vertebrae and a large pygostyle make up the skeleton of the tail. The last but one of these has wide-spreading diapophyses, the others being less prominent in this particular. Adding all these together, w e find that the spinal column of Panyptila contains, besides its pygostyle, thirty-five vertebrae, three more than we found iii the spinal column of Trochilus, which contains but thirty-two. The violet-green Swallow has thirty-five vertebrae in its column, and presumably others of the family have the same. Moreover, the essential characteristics as seen in the ribs, pelvis, and other parts of the axial skeleton also agree. In the short and wide pelvis of Panyptila we find upon superior view open ilio-neural grooves, a small preacetabular area, with the concave surface of the bone, on either side, facing upwards, forwards, and outwards. The postacetabular portions of the ilia are each of a quadrilateral outline, and their superficies uniformly convex. A side view of the pelvis presents a large, elliptical, ischiac foramen, a small cotyloid ring, aud considerable traces of an obturator space, the foot-like process of the ischium meeting the postpubis behind the last. This pattern of the bone is pretty much the same as w e find it in the Swallows (Hirundo, Tachycincta, Petrochelidon, Cotile), the principal differences being, that in the latter group the parial foramina among the sacral transverse processes are always notably large, and the posterior ilio-ischiac margins are notched (barelv perceptible in P. saxatilis) ; both of these characters, especially the last, are well-known Passerine ones. The form assumed by the sternum in Panyptila is shown in figures 1 and 4 of Plate L X . Here, upon the ventral aspect we see |