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Show 898 DR. R. W. SHUFELDT ON THE OSTEOLOGY OF THE [Dec. 1, the essential characters of the basal aspect of the skull as found in the typical Swifts are present in Panyptila, and they perfectly agree in most important points with the same characters as described by Professor Huxley for Cypselus apus (figs. D and E ). The vomer (Vo) is long and narrow, being deeply cleft behind where it straddles tbe rostrum of the sphenoid. Either limit is carried back as far as the palatine head of the corresponding side, with which it firmly articulates, as well as with the initial portion of its ascending process. Anteriorly, the vomer dilates into a horizontal, triangular extremity, the line of the base being in front, its angles just resting, one on either side, on the upper edges of the broad maxillo-palatines, while the apex merges into the cleft portion which extends backwards. A maxilfo-palatine (Mxp) has the form of a spherical triangle, is notably well developed, but does not meet its fellow in the median line, the interval being spanned by the vomer, as just described. The palatines (PI) are principally in two horizontal planes, and either one has a very characteristic form in the Swifts, which is nearly approached by the Swallows. Its inner margin is deeply. cleft, giving rise to an anteriorly directed process that is quite striking in the Cypselidee, though it amounts to nothing more than an exaggeration of a similar condition found in the Passeres. The narrow palatine body merges anteriorly into the premaxillary, and as it passes forwards to do so, underlaps the great tuberous antorbital ; while further on, it shuts out of sight from this view the connection between the vomer and the maxillo-palatine. Another exaggeration of a Passerine character of the palatine, seen in the Swifts, is the form assumed by the postero-external angle of the bone. It is in them produced into a well-marked oblong process directed backwards and outwards (see figs. D, E, and F ). In the Passerine birds generally the palatines have but one point where they come in contact, and this is at their heads under the rostrum, where they articulate with the pterygoids. This applies also to the Swallows, while in Panyptila, and presumably in other Swifts, these bones fail to meet even here, being separated by quite an appreciable interval (fig. D ) . W e have already seen that they are very widely separated in Trochilus at this point. A pterygoid (fig. D, pt) is a very long, slender, and straight rod of bone, having the same essential characters and making the same style of articulations with quadrate and palatine, as in the typical Passerine birds. In most particulars of any importance, so far as the basis cranii, the rostrum, ethmoid, and all other parts of the skull of Panyptila are concerned, they make no great departures from the generalized Passerine skull, and they are by no means very different from such characters as they are found in Hirundo. Indeed, so far as this part of the skeleton goes, m y studies of the osteology of American Cyp-selida and Hirundinida fully confirm Professor Huxley's investigations in that direction, w h o long ago pointed out the close relationship of these two groups of birds (P.Z.S. 1867, p. 452). |