1902.] OSTEOLOGY OF THE FALCONIFORMES. 279 



member of the group. It is continued downwards on either side 

 to form the inner border of the processus alse exoccipitalis inferior 

 (paroccipital process, auct.). 



The lambdoidal ridge is always single and has an undulating 

 outline. It is continued outwards for some considerable distance, 

 when it suddenly bifurcates, one branch running directly outwards 

 and forwards to terminate at the superior angle of the exoccipital 

 wing, at its junction with the squamosal process ; and one directly 

 downwards and outwards to lose itself in the free border of the 

 exoccipital wing near its middle. In Serpentarius^ Polyhoroides, 

 and the Vultures the upper and outer branch is barely perceptible 

 or wanting. In Oathartse there is a deep notch between the 

 bifurcation, so that it appears, at first sight, to be wanting. We 

 may probably regard this as the more primitive form, since 

 the fiUing-in of this notch seems to have been to increase and 

 perfect the tympanic aperture. Beneath the lambdoidal ridge, 

 and on either side of the cerebellar prominence, lies a well-marked 

 depression, the supra- occipital fossse. The latter appear to be 

 best developed in the Falcons. In the Oathartse they take the 

 form of wide channels. 



The exoccipital wing is continued downwards into the processus 

 alee exoccipitalis inferior of Suschkin (paroccipital process, auct.). 

 These will be found most strongly developed in the Oathartfe. 



The exoccipital wings are much more developed in the Striges, 

 where the upper and outer portion of the wing is developed on 

 either side into a prominent, outstanding flabellum. 



The cranial roof (PI. XXXII.). — The cranial roof is never 

 marked by supra- orbital grooves. 



In Serpe7itarius (PI. XXXII. fig. 2) the interorbital region is 

 widened by long, horizontal, backwardly-directed lachryrnal pro- 

 cesses, the inner borders of which are closely applied to the frontal, 

 but do not fuse therewith. In the Cathartse (PI. XXXII. fig. 1) 

 there would appear to have been similar processes, bvit these have 

 now fused completely with the frontal, a row of foramina only 

 indicating their line of junction. 



In the Accipitres (PI. XXXII, fig. 3) these horizontal processes 

 are free, and project on either side of the head, above the 

 orbits. In the Buteonidse there is a small free plate of bone 

 attached by ligament to the end of the horizontal process — the 

 superciliary plate. This plate is probably a remnant of the 

 supra-orbital chain of ossicles such as occurs in some Palseognathfe, 

 e. g. Ti7iamus, Struthio, and in Psophia among the Neognathse. 

 Both the horizontal process and the superciliary plate have under- 

 gone great reduction in the Vultures, Gypohierax alone retaining 

 a small remnant of the accessory plate. This same reduction of 

 the horizontal process is also a mai-ked feature in Polyhoroides, 

 wherein it is almost suppressed ; the descending process of the 

 lachrymal, it may be mentioned in passing, is very long and 

 slender. The lachrymal of Pandion has undergone still further 

 degeneration, having fused completely with the frontals and 



