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Show 1885.] TROCH1LID.E, CAPRIMULGHLE, AND CYPSELIDJE. 897 hypohyals quite long, their cartilaginous ends curling well up behind the skull. Minute cerato-hyals may ossify in Chordediles; but I have not observed them to do so in P. nuttalli. This anterior portion of the apparatus has the arrow-head form seen among the class generally where that part is short, and the glossohyal is not produced far forwards. Of the Cypseline Skull.-Upon a lateral view of the skull of Panyptila saxatilis the external narial aperture is seen to be very large and elliptical in outline. The maxillary process of the nasal descends in a straight line to join the maxillary below, which latter bone, like the premaxillary, is very delicately constructed. I have failed to find a free lachrymal in the Swifts, and if it does occur it is very rudimentary. It is just possible that it may be incorporated with the pars plana, as it is in the Swallows and some other passerine birds. Owing to the narrowness of the mid-frontal region, the orbital cavity, though very capacious, is not relatively so deep as in Chordediles, but has the same general aspect it presents in the Swallows. The interorbital septum usually contains one or two extensive vacuities in it, and the greater part of the tract for the olfactory nerve and its cranial exit is deficient in bony support. The pars plana is of a quadrate outline, very large and, I believe, in all true Cypseline birds, of a tuberous conformation, as it here is in the Rock-Swift. Panyptila has a quadrate-bone in many respects like Chordediles ; the orbital process, however, is very much better developed, though not quite so well as it is in the Swallows, where it wears more the character of the Passeres. The two facets upon the mandibular foot of the bone are almost exactly as we find them in the Night-hawks, while the antero-posterior compression of the body is equally well marked. Two narrow facets are found upon the summit of its mastoidal head. The quadrato-jugal rod is slender and retains a uniform calibre to the maxillo-jugal junction, when it becomes laterally compressed before arriving at the expanded portion. Seen from above, the general contour of the skull of the Rock- Swift closely resembles that of a Swallow ; in the former, however, we find the median portion of the premaxilla constructed upon the same plan as I described it for the Goatsuckers, being reduced to a thread-like rod of bone between the insertion of the nasals behind, and where it merges into the mandibular tip in front. This gradually expands after it passes the former point to make rather a broad insertion as it abuts against the cranio-facial region, leaving, as it does so, a conspicuous triangular vacuity on either hand, between it and the nasals. The cranio-facial region is somewhat concaved, while the interorbital space, upon this aspect of the skull, is narrow, in both of which particulars the Swifts agree with the Hirundinida. The vault of the cranium is smooth and uniformly convex, being barely marked in tbe median line by a longitudinal crease. All of |
