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Show 1902.] OSTEOLOGY OF THE FALCONIFORMES. 287 aperture for the internal carotid. The pathetic lies dorsad of the oculo-motor foramen, and may be continued backwards and downwards by a groove terminating above the orbito-nasal foramen. The cerebral fosses do not lie altogether in front of, but rather exhibit a tendency to overlap the cerebellar fossse. The lateral extension of the cerebral fossse is very marked. The fossae are conspicuously depressed dorso-ventrally. This is most noticeably so in Fcdco : the distance between the point where the right and left tentorial ridges converge to join the median bony falx and the prominent triangular bony boss which bounds the mesencephalic fossa posteriorly being considerably less than in Vultur. The olfactory fossce are represented by a small median pit leading forwards into twTo narrow apertures for the optic nerves. The Premaxilla. The premaxilla, in all the Falconiformes, is more or less distinctly hooked at the tip. In length and stoutness it varies. In the Falcons and Polyborus it is short and wide and much hooked. The tomium, in Falcons, is notched, or rather is provided with a distinct "tooth." The palatal surface in both Falcons and Polyborus is extensive and marked by a well-defined median ridge, passing backwards in the nraxillo-palatine processes. This ridge is faintly represented in Serpentarius. In many Vultures, the palatal surface of the premaxilla is more or- less deeply hollowed (Plate X X X I . fig. 5); the excavation being most noticeable in the larger forms, In others, where the breadth is slender, the palatal surface is but slight, passing rapidly backwards into a groove filled by the ventral border of the nasal septum. In the majority of the Falconiformes, the palatal surface of the premaxilla resembles that of the smaller Vultures-is slight, bifurcate, and filled by the ventral surface of the nasal septum. The Cathartse differ markedly from all the other Falconiformes in the form of the palatal surface of the premaxilla. In these last the body of the premaxilla is very highly pneumatic, a section thereof revealing a mass of cancellated tissue between two dense plates of bone. This increase of pneumatic tissue brings the palatal surface clown close, or very near to, the level of the tomium. In the Cathartse this pneumatic tissue is almost wanting, so that the palatal surface comes to form a vaulted chamber. The resemblance in the structure of the premaxilla to the Tubinares is very striking. The fusion of the nasal processes of the premaxilla with one another and with the nasals is very complete in all the Falconi- TOT*TH6S In Microhierax the beak articulates with the skull by means of a fronto-nasal hinge as in Parrots and some other birds. In the Cathartse the fused lachrymal and frontal combine to |
