OSTEOLOGY 



141 



they are in reality not such hard and fast distinctions ;is 

 might be gathered from the foregoing abstract and from 

 textbooks in general. 



PARKER has distinguished four categories of desmo- 

 gnathism (a) perfect direct, the maxillo-palatines uniting 

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

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

 perfectly direct, maxillo-palatines sutured together in the 



Pm.r 



V,, 



Six 



FIG. 79. SKULL OF Alca, (AFTER HUXLEY). 



*, prefrontal (eetethmoid) ; <IH, quadrate : J/.r. 

 Maxilla. Other letters as in previous figure-.. 



FIG. 80. SKULL OF Corvus (AFTEH 

 HUXLEY). LETTERING AS BEFORE. 



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

 articulated with and separated by the median septomaxillary. 

 There is also the exaggerated desmognathism (' double des- 

 mognathisna ') 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 segithognathous birds (Megalcema), in which the 



