(a) Aegithognathous. Maxillo-palatines not coalesced with 

 each other across the middle line of the palate ; vomer broad and 

 truncated in front (fig. 3, p. 3). 



(b) Schizognathous.M&xillo-p&l&iines not coalesced with each 

 other across the middle line of the palate ; vomer narrow and more 

 or less pointed in front (fig. 4, p. 4). 



FIG. 6. Base of the skull of Cathartes aura, showing the second type of 

 desmognathous arrangement of the palate bones, the maxillo-palatines being 

 united below the ossified nasal septum : mxp, maxillo-palatines ; la, lacrymal ; 

 sph.r sphenoidal rostrum ; pa, palatine ; bptg.pr, basi-pterygoid process 

 of the basi-sphenoid ; ptg, pterygoid. 



(c) Desmognathous. Maxillo-palatines either coalesced across 

 the middle line or united by an ossified nasal septum ; vomer often 

 absent (figs. 5 and 6, pp. 5, 6). 



(d) Dromceognathous. Vomer expanded behind so as to prevent 

 the palatines from articulating with the rostrum of the basi- 

 sphenoid (fig. 7, p. 7). 



VI. The presence or absence'of the basi-pterygoid processes on 



