INTRODUCTORY AND EXPLANATORY xvii 



people who call for easier names do not stop to 

 reflect that, in many cases, the scientific names are 

 no harder than others, simply less familiar, and, 

 when domesticated, they cease to be hard: witness 

 mammoth, elephant, rhinoceros, giraffe, boa con- 

 strictor, all of which are scientific names. And 

 if, for example, we were to call the Hyracothe- 

 rium a Hyrax beast it rvould not be a name, 

 but a description, and not a bit more intelli- 

 gible. 



Again, it is impossible to indicate the period 

 at which these creatures lived without using the 

 scientific term for it — Jurassic, Eocene, Plio- 

 cene, as the case may be — because there is no 

 other way of doing it. 



Some readers will doubtless feel disappointed 

 because they are not told how many years ago 

 these animals lived. The question is often asked — 

 Hoiv long ago did this or that animal live ? But 

 xvhen the least estimate puts the age of the earth 

 at only 10,000,000 years, while the longest makes 

 it 6,000,000,000, it does seem as if it were hardly 

 worth while to name any figures. Even when 

 we get well toward the present period we find 

 the time that has elapsed since the beginning of 



