OSTEOLOGY OF BIRDS IOI 



Mewed upon its upper aspect, this skull is seen to be transversely 

 broad in the frontal region, and handsomely rounded over the vault 

 of the cranium giving evidence of a capacious brain case, which the 

 hawk in reality possesses. The orbit is roomy, and deep ; and the 

 septum partitioning the two cavities usually shows a small, irregular 

 vacuity near its center. A large opening is also found over the 

 broad pars plana leading into the rhinal spaces. The groove for 

 the nasal nerve from the brain case is single, (double in some 

 falcons) and continuing as an open conduit it leads into a small 

 slitlike foramen to the inner side of the last mentioned one. Both 

 squamosal and postfrontal processes are fairly well developed, and 

 the temporal fossa somewhat extensive, and distinctly defined. The 

 auricular aperture is very large, and exposes to view most of the 

 bony structures of the internal ear. 



Turning to the base of this skull, we are to observe that a quad- 

 rate bone is very broad across its body; the orbital process is small; 

 there are two articular facets on the twisted mastoidal head, and 

 finally, its mandibular articulatory surface is wide transversely, nar- 

 row anteroposteriorly, and the cup for the quadratojugal bar looks 

 directly to the front. The zygoma is straight, slender at its maxil- 

 lary end, and stouter behind where it is laterally compressed. Either 

 pterygoid is short and rodlike, being cupped at both extremities. 

 The Eustachian tubes are completely closed in by bone in the adult, 

 the anterior opening being rather large and common to both passages. 

 Well separated in front, but lightly in contact along the rounded 

 rostrum behind, the palatine bones are straight and narrow for their 

 prepalatine parts, while the postpalatine portions, more than double 

 the width of the first named, are characterized by their vertical in- 

 ternal laminae, and completely rounded off posteroexternal angles. 

 Upon the outer margin of a palatine, at the junction of pre- and 

 postpalatine, a distinct little process is always seen in this falcon. 



The vomer is free, straight, transversely compressed, and rod- 

 like, with a slight tendency to bifurcate behind where it articulates 

 with the palatines, and with a nib upon its anterior free end where 

 it rests against the hinder margin of the fused maxillopalatine- 

 septonarial mass. Of a niaxillo palatine it is to be observed that the 

 anterior margin of its horizontal part (which includes the maxillary) 

 is completely fused with the adjacent edge of the premaxillary and 

 other osseous structures in front of it. The vertical portion of 

 the maxillopalatine is a beautiful, nonspongy, shell-like scroll, that is 

 concaved externally, well separated for its posterior moiety from the 



