404 



THE PIGEON. PHYLUM CHORDATA 



brain. The nasal capsules are fused with the interorbital septum. 

 Above them is a pair of nasals, deeply notched in front for the 

 nostrils. The vomers are vestigial in the pigeon, but in the fowl 

 are represented by a slender median rod in front of the rostrum. 

 The upper jaw is completely ossified ; the quadrate is a conspicuous 

 three-branched bone articulated with the squamosal, the ptery- 

 goid, the quadratojugal, and the lower jaw, and from it the 



pterygoid runs forwards and slightly 

 inwards to meet the rostrum. From the 

 pterygoid the palatine continues forwards 

 to the nasal capsule. The quadratojugal 

 is a slender splint running forward to the 

 maxilla, which is also small and lies 

 inside the premaxilla ; on its inner sur- 

 face it has a plate-like projection, the 

 maxillopalatine process. The premaxilla 

 completes the upper jaw ; it has two 

 backwardly directed processes which, 

 with the nasal, enclose the external 

 nostril, and the outer of these runs back 

 outside the front part of the maxilla. In 

 front the premaxilla bears the beak. The 

 connections of the palatines with the 

 pterygoids and of the pterygoids with 

 the quadrates, are articulations, not 

 sutures, so that there is some movement 

 of the upper jaw on the cranium ; in 

 parrots the nasals are also articulated to 

 the frontals, so that when the mouth 

 opens the whole upper jaw is raised. 

 In the slender lower jaw, articular, 

 angular, surangular, dentary, splenial, and in some birds 

 prearticular, elements can be made out. There is a columella 

 auris and a slender, mainly bony, forked hyoid apparatus sup- 

 porting the tongue (Fig. 319). 



Fig. 319. — The hyoid ap- 

 paratus of a pigeon. 



a.c. Anterior comu ; b., body of the 

 hyoid; b.br.i, b.br.2, basi- 

 branchials ; b.hd., basihyoid; 

 p.c, posterior comu. 



LIMBS 



The shoulder girdle contains narrow, sabre-like scapulae, stout 

 coracoids which slope down to join the sternum, and slender 

 clavicles which are joined to each other by a disk-shaped inter- 



