18 FRINGILLIM. 



fore, 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, 6, b t 

 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 

 brought into contact with the pterygoid on its own side, 

 the extreme points of the mandibles were separated late- 

 rally to the extent I have already mentioned, namely, 

 three-eighths of an inch. 



The temporal and pyramidal muscles on the right side 

 of the head, that being the side to which the lower jaw 

 inclined, were considerably larger than those on the left 

 side, as represented in figures 1, 2, and 4, letters a and b, 

 and indicated by their bulk the great lateral power this 

 bird is capable of exerting, to be hereafter noticed. The 

 unusually large size of the pterygoid muscles on each side 

 was very conspicuous, figure 2, letters c, c ; the space for 

 them being obtained by the great distance to which the 

 articulated extremities of the lower jaw were removed, and 

 the food of the bird being small seeds, rendered a narrow 

 pharynx sufficient for the purpose of swallowing. 



The muscles which depress the lower mandible are three 

 in number, only one of which, the great pyramidal, is visible, 

 figures 1 and 4, letter b. This large and strong muscle 

 covers two other small ones, the triangular and square 

 muscles, so called from their peculiar shape. These three 

 muscles, all of which have their origin on the occipital 

 portion of the cranium, are inserted by strong tendons on 

 the under and back part of each extremity of the lower 



