NINTH ANNUAL REPORG. 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 twerity-nine species and subspecies of 
Ratite birds, but the specific differences 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.—A pteria 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 trunci laterale-—This is represented principally by the 
naked under surface of the wings, a condition directly brought 
about by the disuse of those organs and their continual pressure 
