280 MR. W. p. PYCRAPT ON THE [Apr. 15, 



aiitorbital plate (pi^efi-ontal). The hoiizontal process is practically 

 suppressed. 



Tlie fronto- parietal region in Gyjjohierax, Aquila, Falco, 

 Polyhorus, and Milvus, the parietal only in Polyhoroides, Buteo, 

 and Haliaetus, is marked by a shallow median groove. This 

 groove is more or less traceable in all the Accipitres save the 

 Cathartfe and Serpentarius. It is es2:)ecially noticeable in the 

 forms just enumerated. In the Oathartse the roof of the skull 

 presents an evenly rounded surface. The width across the skull 

 at the fronto- parietal region in no case approaches that of some 

 Owls, e. g. Bubo, owing to the smaller size of the postorbital 

 processes. 



The fusion of the nasals with the frontals is complete, and 

 leaves no trace of the line of junction. 



The Base of the Skull. 



The basitemporal plate in Serpentarius only is visibly thickened 

 by pneumatic tissue. In the remaining members of this group 

 it is a thin triangular plate with a slightly concave ventral 

 surface. Posteriorly it is bounded, in the middle line, by a more 

 or less well-marked precondylar fossa. It extends outwards on 

 either side as a wing-like plate to join the inferior wing of the 

 exoccipital process, in Serpentarius, Eagles, Buzzards, Falcons, 

 and Vultures, for instance. But in the Osprey this junction with, 

 the exoccipital — completing the mouth of the tympanic cavity 

 below— is formed only by a thin bar of bone. In certain Vultures 

 and in the Cathartse the hinder angles of this plate appear to 

 terminate in a pair of prominent mammillary processes. They 

 are the dominant features of this region of the plate, and by 

 their great size have come to lie behind the actual posterior angles. 

 The two sides of this triangular plate may have sharply defined 

 free edges, e. g. in Aquila, in which case the Eustachian channels 

 are open grooves ; or they may be partly fused with ossified, 

 connective tissue forming the anteiior wall of the recessus 

 tympanicus anterior, when the grooves are partly closed, e. g. 

 Serpentarius, Haliaetus, Buteo] or they may fuse throughout 

 with the inferior border of the wall forming the above-mentioned 

 recess, leaving only a small Eustachian aperture at the apex of 

 the triangle, as in the Oathartas and Polyhoroides, for instance. 

 In the Cathartse the parasphenoidal rostrum immediately above 

 this aperture is deeply excavated. This is especially marked in 

 Sarcorhamphus. 



The parasphenoidal rostrum may or may not bear basipterygoid 

 processes. These are largest in Serpentarius, where they lie at 

 the base of the rostrum. In the Cathartse they may be either 

 short and broad, as in Catharistes and Gypagus, or very slender 

 and seated further forward on the rosti-um, as in Pseudogryphus 

 and Sarcorhamphus (Condor). This greater slenderness evidently 

 marks the first stages in theii' decay. In a skull of Sarcorhamphus 



