286 THE ANATOMY OF VEETEBRATED ANIMALS. 



and unites with tlie maxilla. The two bones are very early 

 represented by one continuous ossification. 



The vomers vary more than almost any other bones of the 

 skuU. They imderHe and embrace the inferior edge of the 

 ethmo-presphenoidal region of the basis cranii, and, in all 

 birds in which they are distinctly developed, except the 

 Ostrich, they are connected behind with the palatine bones. 

 In most birds, they early unite into a single bone; but 

 they remain long distinct in some CcyracotnorpluB, and seem 

 to be always sejiarate in the Woodpeckers. The coalesced 

 vomers constitute a very large and broad bone in most 

 MatitcB, and in the Tinamoinorphce ; a narrow elongated bone 

 pointed in front in Schizogtmthce ; a broad bone deeply cleft 

 behind, and abruptly truncated in front, in Coracomorphce. 

 In most DesmognathcB the vomer is small ; and, sometimes, 

 it appears to be obsolete. 



The maxillse of birds are usually slender, rod-like bones, 

 articulating by squamous suture, in front, with the pre- 

 maxillse, and, behind, with the equally slender jugals. In 

 the great majority of birds the maxilla sends inwards a 

 maxillo-palatine process (Fig. 82, mxp.), which, sometimes, 

 is mere thin lamella of bone, sometimes, becomes swoEen 

 and spongy. In the RatitcB and the Desjnognathce (Fig. 84), 

 the maxillo-palatine processes unite with the vomer, or with 

 one another, and form a complete bony roof across the 

 palate. In the Schizognathce (Fig. 82), and ^githognathce, 

 the maxillo-palatines remain quite distinct both from one 

 another and from the vomer. 



The quadrato-jugal is usually a slender rod of bone, the 

 hinder extremity of which presents, on its inner side, an 

 articular head which fits into a fossa in the outer face of 

 the distal end of the quadrate bone. 



The palatine bones are generally long and concave on 

 their palatine faces. In front, they pass beneath {i.e., on 

 the ventral side of) the maxillo-palatines and unite with 

 the premaxillse, sometimes by a squamous suture, some- 

 times by ankylosis, rarely, as in the PaiTots, by a flexible 

 joint. Posteriorly, they always unite with the ptery- 



