How the History of the Hast Is Head 



time camels, horses, and elephants were among 

 the common animals of North America ; but if 

 we go back to the Eocene we find the group 

 represented in our continent by just three 

 specimens, and two of these seem to have been 

 much like modern birds. The Cretaceous has 

 yielded more specimens and more species, but 

 the bii'ds of that day were totally unlike those 

 of the Eocene, for they were birds with teeth, 

 and we can not trace the connection between 

 them. And here the record ceases, so far as 

 North America is concerned, for back of that 

 we have absolutely nothing. And yet birds 

 there were, because our toothed water-fowl rep- 

 resent two groups, one of which had become so 

 specialized for aquatic life that it had lost the 

 power of flight, and almost lost every vestige 

 of wings. The older rocks (Jurassic) of Eu- 

 rope have yielded two birds, besides a single 

 feather, and these differ as widely from our 

 toothed species as do those from the birds of 

 to-day. The wonder is, not that we know so 

 little of the life of the past, but that we know 

 so much. 



27 



