BIRDS OF OLD 61 



when the mounting of the skeleton had advanced further 

 it became more 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 un- 

 comfortable. And so, at the cost of some little time and 

 trouble, 1 the mountings were so changed that the legs 

 stood out at the sides of the body, as shown in the 

 picture, a position that was verified later on by the 

 discovery of the specimen now in the American Mu- 

 seum of Natural History in which the limbs lay in just 

 the position given them by Mr. Gleeson. 



A final word remains to be said about toothed birds, 

 which is, that the visitor who looks upon one for the 

 first time wiU probably be disappointed. The teeth are 

 so loosely implanted 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 change has taken place in 

 them since that time; they seem to have become so 

 exactly adapted to the conditions of existence that no 

 further modification has taken place. This may be ex- 

 pressed in another way, by saying that while the Mam- 

 mals of the Eocene have no near relatives among those 

 now living, entire large groups having passed completely 



'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, but they 

 are so brittle and heavy that often they will not sustain their own weight. 

 Hence such bones must be supported from the outside, and to do this so 

 that the mountings wUl be strong enough to support their weight, allow 

 the bones to be removed for study, and yet be inconspicuous, is a difficult 

 task. 



