1867.] 



PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. 



425 



2. The long axes of the adjacent parts of the scapula and coracoid 

 make an acute or a slightly obtuse angle, and are never, even ap- 

 proximately, identical or parallel*. The scapula always has a di- 

 stinct acromion and the coracoid a clavicular process. 



3. The vomer is comparatively small, and allows the pterygoids 

 and palatines to articulate directly with the basisphenoidal rostrum f. 



In this order the bones which enter into the formation of the 

 palate are disposed in four different modes, which may be called re- 

 spectively the DromcBognathous, Schizognathous, Desmognathous, 

 and ^githognathous arrangement. 



I. The DromfBognathous Birds are represented by the single genus 

 Tinamus, which (as Mr. Parker has shown ;f) has a completely stru- 



Fig. 5. 



Under view of the skull of Tinamus robushis. From a specimen belonging to 

 W. K. Parker, Esq., F.R.S. 



The letters as before, except * the prefrontal, and + the basijiterygoid, process. 



thious palate. In fact the vomer is very broad, and in front unites 

 with the broad maxillo-palatine plates, as in Dromceiis ; while behind 



* The only genera in which, so far as I know, this angle is somewhat greater 

 than a right angle are Ocydromus and Didus. 



f Tinamus perhaps affords an exception to this character. 



X "On the Osteology of the GalHnaceous Birds and Tinamous " (Transactions 

 of the Zoological Society, vol. v., 1864). Sundevall, however, had already said of 

 Tinamus, Rhijnchotus, and Cri/pturus, " Struthiones parvos referunt." 



