82 ANIMALS OF THE PAST 
those of the leg as to turn edgewise as the foot 
was brought forward and thus to offer the least 
possible resistance to the water. It is a re- 
markable fact that the leg bones of Hesperornis 
are hollow, remarkable because as a rule the 
bones of aquatic animals are more or less solid, 
their weight being supported by the water; but — 
those of the great diver were almost as light as _ 
if it had dwelt upon the dry land. That itdid 
not dwell there is conclusively shown by its 
build, and above all by its feet, for the foot of 
a running bird is modified in quite another 
way. 
The bird was probably covered with smooth, 
soft feathers, something like those of an Apte- 
ryx ; this we know because Professor Williston 
found a specimen showing the impression of 
the skin of the lower part of the leg as well as 
of the feathers. that covered the “thigh” and 
head. While such a covering seems rather in- 
adequate for a bird of such exclusively aquatic 
habits as Hesperornis must have been, there 
seems no getting away from the facts in the 
case in the shape of Professor Williston’s spec- 
imen, and we have in the Snake Bird, one of 
