420 PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. [Apr. 1 1, 



Fig. 1. 



Fmx 



Under view of the skull of Birxdhio cavielus. From a specimen in tlie Museum 

 of the Eoyal College of Surgeons. 



Pmx. The priemaxillfc. B. The sphenoidal rostrum. Vo. Tlie vomer. JV. The 

 palatine bone. M.vp. The maxillo-palatine plate of the maxillary. Pt. The 

 pterygoid. 



A second group is represented by the South American genus Rhea, 

 in which — 



1. The maxillary processes of the palatines are short, and unite 

 with the inner and posterior edges of the maxillo-palatines. 



2. The maxillo-palatines are thin, fenestrated plates, which do not 

 articulate with facets on the edges of the vomer. 



3. The vomer is as long as it usually is in birds, and articulates 

 behind with the palatine and pterygoid bones. 



