OCR Text |
Show 1885.] TROCHILIDJE. CAPRIMULGIDiE, AND CYPSELID.E. 891 for each type, and conclude the descriptive part of the paper with a comparison of the bones of the limbs. Finally, analytical tables will be presented contrasting the essential osteological characters of the several forms that have been examined. Of the Skull in certain Caprimulgine Birds (Plate LIX. figs. 1-4).-It is hardly necessary for me to say that the skull of any Nightjar is as different from that part of the skeleton in Trochilus as this structure can well be in any two existing types of birds. Indeed, so great are the differences, and extended to so many of the parts, that I do not feel called upon to institute a comparison between the two-as this can better be done by the reader for himself from the figures in the Plates-but simply present here a description of the more important of these characters, comparing them, so far as my material will permit, with forms more or less nearly related, as well as with the corresponding characters as they occur in several species of the group. To this end m y material affords a full series of skeletons of the several representatives of the genus Chordediles and some excellent skeletons of Phalanoptilus nuttalli. Regarding the skull of G. texensis from a lateral view (fig. 1), we are struck with the peculiarly arched culmen formed by the median portion of the premaxillary, which is simply a delicate, laterally compressed rod connecting the mid point of the basal region with the apex of the beak. Such a condition is approached also by many Swifts; and in Nuttall's Whippoorwill the valley which is found on either side of this arch harbours the peculiar tubular nostril of that bird. The superior mandible, as a whole, is somewhat decurved, with cultrate margins. A lacrymal is a large and freely articulated bone ; above, its upper surface contributes no little amount to the general frontal area. In this latter region its inner margin is convex and closely applied throughout its extent to the opposed concave edge of the combined frontal and nasal elements. Mesially and on the anterior wall of the orbit, the lacrymal rests upon the upper border of the pars plana, while on its outer aspect it presents a longitudinal and shallow groove. Its lower part is foot-like in form, directed backwards, and is in contact with the maxillary bar. The form and method of articulation of the lacrymal in P. nuttalli is essentially the same as in the last species; but its descending limb has its foot portion T-shaped, and the anterior or heel-process is lodged in the broader part of the maxillary bone. The orbital cavity in the Caprimulgida is particularly notable for the completeness of its bony walls. It is large among the Whippoor-wills, but very strikingly so in the Night-hawks. So far as I have examined the interorbital septum, it is very thick from side to side, though composed of a delicate diploic tissue, which is continuous in structure with that found about the brain-case and in the ethmoidal region, it all being overlain by a firm compact film. |