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, 
a aed oes EU 
Rchikekeda =" os 
ae nines i 
ee pea 
Fic. 2.—Lower jaw of Ichthyornis (after Marsh). 4/5 natural size. 
Fic. 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 
