36 MORPHOLOGY OF THE VERTEBRATA. 



fossa, for the articular head on the inner side of the distal end 

 of the quadrate bone. The quadrate is the moveable bone by 

 which the lower jaw articulates with the skull. It is articulated 

 in front with the prootic, alisphenoid, and squamosal; while its 

 distal end articulates with the mandible below — the pterygoid on 

 the inner, and the quadrato-jugal on the outer side. 



THE QUADRATO-JUGAL 



Is a long and very slender bone, situated below the orbit. Pos- 

 teriorly it presents an articular head, which is received into a 

 fossa on the outer distal end of the quadrate. In front, it is con- 

 nected with the maxilla. 



From this arrangement it follows that when the mandible is 

 depressed, the quadrate is thrown forward, which movement 

 causes the quadrato-jugal and maxilla to move upward and' 

 forward; at the same time the pterygoids and palatines glide 

 forward upon the basisphenoidal rostrum — thus it comes about 

 that the beak is elevated when the pigeon opens its mouth. 



THE SQUAMOSAL 



Is chiefly appliedto the side of the, skull, and is anchylosed to the 

 other bones. 



THE VOMERS 



Are early united into a single bone. It is narrow and elongated, 

 and in front it is pointed. Behind it is connected with the 

 palatines. The posterior nares lie between the palatines and the 

 vomer. 



The eustachian tubes run through the basisphenoid, and open 

 by a common aperture upon the middle of the under surface of 

 the skull. 



THE BEAK 



Consists of an upper mandible, supported by the maxillae and 

 premaxillge, and of a lower mandible formed by the lower jaw. 

 These bones are provided with a sheath of horny fibrous tissue 

 in place of teeth — this sheath being moulded to the shape of the 

 osseous mandibles. 



THE SENSE OF TASTE 



Is imperfectly developed in the pigeon, as in other birds which, 

 having no masticatory organs, swallow their food almost as soon 

 as it is seized. Digitized by Microsoft® 



