18 FRINGILLID^E. 



well as the magnitude of the processes of the bones of the 

 head are also peculiar to this bird. 



The pterjgoid processes of the palatal bones are consi- 

 derably elongated downwards, as shown at figure 3, letter 

 a, to afford space for the insertion of large pterygoid mus- 

 cles. The os omoideum on each side, figure 3, letter #, is 

 strongly articulated to the os quadratum, figure 3, letter 

 (?, affording firm support to the moveable portion of the 

 upper mandible. Letters d, d, refer to the jugal bone, 

 which, united to the superior maxillary bone in front, is 

 firmly attached by its posterior extremity to the outer side 

 of the os quadratum ; when, therefore, the os quadratum 

 is pulled upwards and forwards by its own peculiar mus- 

 cles, to be hereafter mentioned, the jugal bone on each side 

 by its pressure forwards elevates the upper mandible. 



The inferior projecting process of the os quadratum, to 

 which the lower jaw is articulated, in most other birds is 

 somewhat linear from before backwards, and compressed 

 at the sides, admitting vertical motion only upwards and 

 downwards ; the same processes in the Crossbill are sphe- 

 rical, as shown at figure 3, letter c ; the cavity in the 

 lower jaw destined to receive this process is a hollow cir- 

 cular cup, figure 5, letter a ; the union of these two portions, 

 therefore, forms an articulation possessing much of the 

 universal motion and flexibility of the mechanical ball and 

 socket joint. 



The lower jaw is of great strength, the sides or plates 

 elevated, with prominent coronoid processes, figure 5, #, 5, 

 to which, as well as to the whole outer surface of the plates, 

 the temporal muscle is attached ; and in a head of this 

 bird, which had been divested of all the soft parts, I found, 

 on sliding the lower jaw laterally upon the upper, as per- 

 formed by the bird, that before the coronoid process is 



