NINTH ANNUAL REPORT. 227 
ment of the eye. It, however, 
naturally lacks the delicate 
adjustment of the eyes of a 
bird such as a hawk, which 
can become near-sighted or 
far-sighted at will. 
As in cursorial mammals, 
the general contour of the 
body of these birds is adapted 
to lessen resistance to the air. 
Yet in the present connection 
no stress can be laid upon this 
character, since the ratite birds 
are descended from true birds 
of flight, with keeled sternums 
and a general moulding of the 
body even more adapted for 
swift motion through the air. 
The enormous weight of some FOOT OF THE APTERYX. 
of the ratite birds is a condition 
impossible in a flying bird. A full-grown Ostrich may weigh 
three hundred pounds; while twenty-five pounds for a swan and 
thirty-two pounds for a bustard are maximum weights among 
the volant Carinatae. 
Any extensive mention of the skeletal adaptations would be 
foreign to this paper, and indeed, when we study the bony frame- 
work of the struthious birds, we find so many characters which 
are dinosaurian and typically reptilian, that it seems as 1f any 
phylogenic comparison must be with the Sawropsida as a whole, 
rather than with Archaeopteryx or the Carinatae alone. 
The most important changes in the skeleton, due to the cur- 
sorial habits of these birds, are plainly visible on the exterior. 
One feature is the long and flexible neck, correlated with the long 
legs. The swan is the only carinate bird which equals the Ostrich 
in the number of cervico-dorsal vertebrae, each having twenty- 
five. 
The tall casque, or horny helmet, of the Cassowary, supported 
by osseus tissue within, is a special adaptation to protect the 
bird’s head from the many hanging lianas and the undergrowth 
which it encounters when leaping and running at full speed 
through the dense forests of its haunts. 
The flat, camel-like resting-pad of the Ostrich reveals the char- 
acter which has given the name of Ratite to this Subclass of birds 
