BIRDS OF OLD 85 



evident that Hesperornis was not an ordinary 

 bird, and that he could not have swum in the 

 usual manner, since this would have brought his 

 great knee-caps up into his body, which would 

 have been uncomfortable. And so, at the cost 

 of some little time and trouble,* the mount- 

 ings were so changed that the legs stood out at 

 the sides of the body, as shown in the picture. 



A final word remains to be said about 

 toothed birds, which is, that the visitor who 

 looks upon one for the first time will probably 

 be disappointed. The teeth are so loosely im- 

 planted in the jaw that most of them fall out 

 shortly after death, while the few that remain 

 are so small as not to attract observation. 



By the time the Eocene Period was reached, 

 even before that, birds had become pretty 

 much what we now see them, and very little 



* The mounting of fossil bones is quite a different matter 

 from the wiring of an ordinary skeleton, since the bones are not 

 only so hard that they cannot be bored and wired like those of a 

 recent animal, bid they are so brittle and heavy that often they 

 will not sustain their own weight. Hence such bones must be 

 supported from the outside, aud to do this so that the mountings 

 will be strong enough to support their weight, allow the bones to 

 be removed for study, and yet be inconspicuous, is a difficult task. 



