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THE AMERICAN NATURALIST. [Vol. XXXVII. 



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 articu- 

 lates behind with the palatine and pterygoid bones. 



4. The prefrontal processes are little ossified. 



5. The bodies of the proper sacral vertebrae do not unite 

 with the pubes or ischia ; and the centra of the sacral vertebrae, 

 which ossify late, are extremely elongated and slender. 



6. The short sternum narrows posteriorly and presents a 

 notch in the middle of its posterior edge. 



7. The length of the humerus exceeds the distance between 

 the shoulder girdle and the ilium, and is of course greatly longer 

 than the scapula. The manus has the same conformation as 

 that of Struthio. 



8. The pubes are free, but the ischia unite beneath the 

 urosacral vertebrae. 



9. The hallux is absent, but the second, third, and fourth 

 digits are complete. 



10. There are only thirty-two precaudal vertebrae. (Proc. 

 Zool. Soc, 1867, pp. 420-422.) 



As in the case of Struthio, the skeletology of Rhea has long 

 been known, and Prof. Kitchen Parker has, in his famous paper 

 " On the Osteology of Gallinaceous Birds and Tinamous," given 

 us a few of the necessary characters for the use of the taxon- 

 omer, they being presented in connection with what is there 

 done with Tinamus. 



The late T. J. Parker compared the skulls of Struthio and 

 Rhea in his memoir on the Dinornithidae (see anted), and showed 

 that the differences existing between these two birds, in so far 

 as that part of the skeleton is concerned, was in his estimation 

 of ordinal rank. These distinctions, however, in the present 

 work are considered to be but of subordinal value. 



Suborder III. Casuariornitb.es. 



Families: Dromaiid^ (the emeus) ; Casuariid^e (the cassowaries); 



DromornithiDjE (extinct). 

 Huxley has already pointed out {Proc. Zool. Soc, 1867, pp. 

 422, 423) that the osteology of Casuarius and Dromseus (emeu) 



