NINTH ANNUAL REPORT. 217 



The struthious birds stand alone in the extent of their fitness 

 for a terrestrial, and a defensive-cursorial life; and this change 

 in habits has brought about many interesting structural adapta- 

 tions. There are some twenty-nine species and subspecies of 

 Ratite birds, but the specific difit'erences are of minor importance. 

 In every case I have found it desirable to speak of the Ostrich, 

 the Cassowary, the Emeu, etc., making the collective name stand 

 for the group, and ignoring, in the present connection, all specific 

 characteristics. I have confined myself entirely to the considera- 

 tion of external adaptations — those which any visitor to the Zoo- 

 logical Park may observe for himself. 



The characteristics peculiar to birds of the Subclass Ratitae 

 may be divided into three classes : 



1. Characters due to an early breaking away from the more 

 typical avian stem. (These consequently are almost entirely 

 reptilian.) 



2. Characters which are directly due to a change from an 

 arboreal, volant life to one wholly terrestrial and cursorial. 



3. Characters which are indirectly due to this change in life 

 habits. 



In treating of the subject of this paper, I have not undertaken 

 to divide the characters in this manner, but will briefly review 

 them in anatomical sequence, as follows : 



I. Integument. 



A. Pterylosis (distribution of feathers in tracts). 



B. Remiges (flight-feathers of wings). 



C. Rectrices (rudder-feathers of tail). 



D. Body Feathers. 



E. Claws and Scales. 



II. General Form. 



I. INTEGUMENT. 



A. Pterylosis. — Apteria mesogastraei. — This consists chiefly of 

 the sternal callosity, or kneeling pad, of thick skin, on which these 

 birds rest when lying prone upon the ground — the natural sleep- 

 ing posture of Ostriches, Rheas, Emeus and Cassowaries. This 

 habit, directly consequent upon their terrestrial life, would thus 

 tend to keep this tract bare of feathers, even though elsewhere on 

 the body the apteria inherited from volant ancestors should be- 

 come all but obliterated. 



Apteria truuci latcralc. — This is represented i)rincipally by the 

 naked under surface of the wings, a condition directly brought 

 about by the disuse of those organs and their contiiuial pressure 



