52 THE CLASSIFICATION OF BIRDS 



STRUTHIONIFORMES. 

 31. STRUTHIONES. 



The Dromgeomorphge contain four families, which differ from each 

 other very widely. The feet of the Apterygidce may be regarded 

 as normal ; the Eheidce and the Casuariidce have lost the hallux ; 

 whilst the Struthionidce have not only lost the hallux, but also the 

 second digit. The Struthionidce differ from the other three families 

 in having the vomer abruptly truncated posteriorly instead of being 

 produced and bifurcated to coalesce with the palatines and ptery- 

 goids. The Eheidce differ from the other three families in having 

 the vomer free from the maxillo-palatines. The Apterygidce may 

 be regarded as normal in having the bridge over the extensor digi- 

 torum on the tibia ossified, which is not the case in the other 

 three families. The Casuariidce and the Apterygidce have a much 

 shorter humerus (less than the combined length of four dorsal 

 vertebrae) than the Eheidce and the Struthionidce (more than the 

 combined length of six dorsal vertebrae). The Eheidce differ from 

 the other three families in having a pair of tracheo-bronchial 

 muscles. 



The Apterygidce inhabit New Zealand, the Casuariidce Australia, 

 the Struthionidce Africa, and the Eheidce South America. 



