318 THE A 7 ERTEBRATE SKELETON. 



lying ventral to the anterior continuation of the interorbital 

 septum. 



The bones of the upper jaw consist on each side of two 

 slender arcades which in front converge and are attached to 

 the large beak, while behind they diverge but are united by 

 the quadrate. 



The inner arcade is formed by the pterygoid and palatine. 

 The pterygoid (fig. 60, 21) is a short flattened bone, which 

 articulates behind with the quadrate, and on its inner side 

 with a large flattened surface borne by the rostrum, in front 

 it meets the palatine, or sometimes ends freely with a long 

 antero-dorsally directed point. 



The palatine (fig. 60, 20) is a slender irregular bone flat- 

 tened dorso-ventrally at its anterior end where it articulates 

 with the beak, and laterally behind. It gives off at its 

 posterior end a process, which is sometimes united with the 

 vomer, sometimes projects forwards, and meets its fellow 

 dorsal to the vomer. In the large space between it and the 

 vomer is the opening of the posterior nares. 



The premaxillae (figs. 59 and 60, 2) are very large, and 

 form nearly a third of the big shovel-shaped beak. They con- 

 stitute the inner, and part of the front boundary of the an- 

 terior nares, and send back a pair of nasal processes which 

 partially separate the nasals from one another. 



The outer arcade forms the slender suborbital bar, 

 and consists mainly of two rod-like bones, which in the adult 

 are completely fused together. The posterior of these is the 

 quadratojugal (figs. 59 and 60, 11) which articulates with tlie 

 quadrate, the anterior is the small and slender jugal or malar 

 (figs. 59 and 60, 10). The extreme anterior part of the bar is 

 formed by the maxilla. The main part of the maxilla how- 

 ever lies anterior to the suborbital bar, and extends forwards 

 along the side of the premaxilla forming all the lateral part of 

 the beak (figs. 59 and 60, 1); it also sends inwards a plate, 

 the maxillo-palatine (fig. 60, A, 29), which completely fuses 



