90tj 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 

 thein), 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 

 vertebrjE are true dorsals, having perfect ribs connecting them with 

 the sternum ; and they have low neurid spines which interlock with 

 each other at their ends, these vertebrae all being freely movable 

 upon one another. 



Nothing of special importance characterizes these ribs ; all have 

 strong epipleural appendages anchylosed to them, save the last pair, 

 in wliich they are absent. Two pairs of feeble ribs also sjiring from 

 beneath the sacrum, the hinder pair being very rudimentary in some 

 specimens. 



From the twentieth to the twenty-ninth vertebrcC, all inclusive, 

 are firmly anchylosed together to form the pelvic sacrum. To their 

 outer common diapophysial margins, the ilia make thorough con- 

 nection, 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, we find that the spinal column of 

 Panyptila contains, besides its pygostyle, thirty-five vertebrae, three 

 more than we found in the spinal column of Trochilus, which contains 

 but thirty-two. 



The violet-green Swallow has thirty-five vertebrae in its column, 

 and presvimably others of the family have tiie 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, elhptical, ischiac fora- 

 men, a small cotyloid ring, and 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 we find it in 

 the Swallows {Hirundo, Tachycincta, Petrochelidon, Cotilc), the 

 principal differences being, that in tlie latter group the parial fora- 

 mina among the sacral transverse processes are always notably large, 

 and the posterior ilio-ischiac margins are notched (barely 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 LX. Here, upon the ventral aspect we see 



