1902.] OSTEOLOGY OF THE FALCONIFORMES. 287 



aperture for the internal carotid. The pathetic lies doi'sad of the 

 oculo-motor foramen, and may be continued backwards and down- 

 wards by a groove terminating above the oi'bito-nasal foramen. 



The cerebral fossce do not lie altogether in fi'ont of, but rather 

 exhibit a tendency to overlap the cerebellar fossa?. The lateral 

 extension of the cerebral fossae is very marked. The fossae are 

 conspicuously depressed dorso-ventrally. This is most noticeably 

 so in Falco : the distance between the point whei-e the right and 

 left tentorial ridges converge to join the median bony falx and 

 the prominent triangular bony boss which bounds the mesen- 

 cephalic fossa posteriorly being considerably less than in Vultur. 



The olfactory fossce are represented by a small median pit 

 leading forwards into two narrow apertures for the optic nerves. 



The Preinaxilla. 



Tlie pre«i««i7^a, in all the Falconiformes, is more or less dis- 

 tinctly hooked at the tip. In length and stoutness it varies. 



In the Falcons and Polyhorits it is shoi-t 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 Polyhorus is extensive and marked by a well-defined 

 median ridge, passing backwards in the maxillo-palatine processes. 

 This ridge is faintly i-epresented in Serpentarius. 



In many Vultures, the palatal surface of the premaxilla is more 

 or less deeply hollowed (Plate XXXI. fig. 5) ; the excavation 

 being most noticeable in the lai-ger 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 Oathai-tfe 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 down 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 pre- 

 maxilla 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- 

 formes. 



In Microhierax the beak articulates with the skull by means of 

 a fronto-nasal hinge as in Parrots and some other birds. 



In the Cathartfe the fused lachrymal and frontal tiombine to 



