BIRDS OF OLD 59 



muscles to dwindle, and besides artificial selection, the 

 breeding of fowls for food has kept up the mere size of 

 the muscles, although these lack the strength to be 

 found in those of wild birds. 



As a swimming bird, one that swims with its legs 

 and not with its wings, Hesperornis has probably never 

 been equalled, for the size and appearance of the bones 

 indicate great power, while the bones of the foot were 

 so joined to 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 remarkable 

 fact that the leg bones of Hesperornis are hollow, re- 

 markable 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 it did 

 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 Apteryx; 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 

 inadequate 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 specimen, and we have in the Snake Bird, 

 one of the most aquatic of recent birds, an instance of 

 similarly poor covering. As all know who have seen 

 this bird at home, its feathers shed the water very im- 

 perfectly, and after long-continued submersion become 

 saturated, a fact which partly accounts for the habit the 

 bird has of hanging itself out to dry. 



