Ancestors 5 



literally fly through the water by means of their flipper- 

 like wings. 



The large size of the leg and toe bones of Hesperornis 

 shows that great speed was attainable in the water, 



Fig. 2. — Lower jaw of Ichthyornis (after Mar.sh). 4/5 natural size, 



Fig. 3.— Lower jaw of Alligator. 1/6 natural size. The teeth are set in distinct 

 sockets both in the extinct bird and in the living reptile. 



while only a single bone remained to show where the 

 wings of its ancestors were situated. It is doubtful if it 

 could stand erect upon land, being in this respect more 

 helpless even than a grebe. Its nest, if it made one, 

 must have been at the very edge of the shore, from which 



