b PICAEiai 



(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). 



(&) Schizognathous. — Maxillo-palatines 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). 



6j:>ta.fir; 



Fig. 6. — Base of the skull of Catha/rtes 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 sphenoiSal rostrum ; pa, palatine ; b.ptg.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 



