454 



AVES. 



differences between many of them are slight and "the classifi- 

 cation presents considerable difficulties. 



The system here adopted, which in its main feature is that of 

 Fiirbringer and Gadow, is as follows : — 



Order 1. Archaeornithes, 

 Order 2. Neornithes. 



It must not be supposed that the divisions here called orf iers, 

 and sub-orders at all correspond in value with the similarly 

 named divisions in other classes ; for as already pointed out (p. 

 417) the differences between them are hardly if at all greater 

 than those which distinguish families in other classes of Verte- 

 brata. 



Order 1. ARCHAEORNITHES (SAURURAE). 



This order contains only one genus, the extinct Archacopteryx 

 V. Meyer from the lithographic slates of Solenhofen (Upper 

 Jurassic). 



Archaeopteryx is the oldest known bird and possesses most of 

 the features of avine specialisation. The peculiar characters 



