PHTLOGENY OF THE PLJEOGNATH^E AND NEOGNATH.E. 183 



In Drommus the beak is flattened dorso-ventrally. The premaxillary body is larger 

 than in Casuarius, and, as in this genus, the rod-like nasal process seems to be 

 continued forwards to the tip of the beak by reason of paired lateral grooves which 

 divide it from the maxillary processes. 



The nasal process is relatively longer than in Casuarius. Posteriorly it is received 

 into a shallow groove excavated out of the median borders of the nasals. The tip of 

 its free end rests upon the mesethmoid. 



The maxillary processes are splint-like, and extend backwards to the level of the 

 anterior region of the orbit — beyond the body of the lachrymal. 



The palatine processes are short pointed lamellae, rather more widely separated one 

 from another in the middle line than in Casuarius. The chink-like anterior* palatine 

 foramen is closed caudad, as in Casuarius, by the vomer. This process extends 

 backwards as far as the level of the anterior border of the posterior narial aperture. 

 In Casuarius, it should be mentioned, it falls short of this. 



In Dinornis the median nasal process is markedly flattened and expanded dorso- 

 ventrally. The maxillary processes are very short, not extending backwards beyond 

 the level of the hinder end of the antorlital fossa. 



The palatine processes take the form of flattened laminae, extending backwards, as in 

 Dromceus, to the level of the anterior end of the posterior nares. The alveolar borders 

 are deeply pitted. 



The anterior palatine foramen is small and cordiform. It is closed above by the 

 parasphenoid rostrum, and posteriorly by the vomer. In Emeus it is more completely 

 closed than in any other Palceognathce by a pair of processes from the postero-internal 

 angles of the palatine processes, which meet in the middle line, serving at the same 

 time as articular surfaces for the anterior ends of the probably paired vomers. 



The prenarial septum is most clearly marked in Dinornis. Its postero-ventral 

 border is bilaminate, but the laminse rapidly fuse to form the single median vertical 

 septum. 



In JEpyornis the nasal process rises sharply from the body of the bone, giving the 

 beak a peculiar conical form. The alveolar border is deeply pitted. The backward 

 extensions of the palatine and maxillary processes cannot be made out in either 

 the British Museum skull or that belonging to the Hon. Walter Rothschild. In the 

 British Museum skull there is a prenarial septum, but the laminse composing this 

 have not fused to form a median plate as in Dinornis. Instead, as indicated, they 

 remain widely separated, and enclose between them a long tunnel-like cavity extending 

 forwards to the tip of the beak. 



In Rhea the premaxillary body is of greater length than in any other Ratite, and 

 much depressed dorso-ventrally. It is grooved dorsally on either side of the distal end 

 of the nasal process, as in the other forms. 



The nasal process is very broad and flattened, but tapers more or less caudad 



2i)2 



