8 AYES. 



presence oi' al)senc'e of a median keel to the sternum. But these 

 groups, though accepted by Blanford and Gates, are very un- 

 satisfactory, since in some fiiglitless Carinatce the sternum has 

 become reduced to the Katite condition. 



Taking into consideration birds both livingand extinct, we have 

 two well-delined sub-classes, the Arcliceoraithes and JSeornithes. 



inxjt 



P^'J-r 



Under view of the skull of a Eaven. vo, Vdiner; inxp, niaxillo-iDalatine 

 process; ^w, palatine; ptg, pterygoid; </, quadrate; h.^iuli, basi-spbeiioid ; 

 sph.r, spheu(jidal rostrum. 



The first is reserved for the Arclmopteryx with an elongated 

 reptilian chain of caudal vertebrae, each bearing a pair of rectrices 

 and having the jaws armed \^ith teeth. The sub-class JSeornithes 



