OSTEOLOGY 



141 



they are in reality not such hard, and fast distinctions as 

 might be gathered from the foregoing abstract and from 

 textbooks in general. 



Paekbe has distinguished four categories of desmo- 

 gn£ithism^(a) perfect direct, the maxillo-palatines uniting 

 below in the middle line ; (&) perfect indirect, maxillo- 

 palatines separated by a chink in the middle line ; (c) im- 

 perfectly direct, maxillo-palatines sutured together in the 



Fig. 79. — Skull of Alca (aftek Hdxley). 



*, prefrontal (ectethmoid) ; Qu, quadrate ; Mx, 

 Maxilla. Other letters as in previous figures. 



Pig. 80, — Skull of Corvus (afteb 

 Huxley). Lettebing as befoke. 



middle line ; (d) imperfectly indirect, maxillo-palatines closely 

 articulated with and separated by the median septomaxillary. 

 There is also the exaggerated desmognathism (' double des- 

 mognathism ') of the hornbills, &c., where not only the 

 maxillo-palatines but also the palatines are united across the 

 middle line ; and finally the spurious desmognathism of 

 ■certain aegithognathous birds (Megalmma), in which the 



