TREFACE TO THE FIRST EDITION. v ii 



hands of different writers. The order which I have adopted I know is 

 not free from objection on this score, but it seemed to me, on the 

 whole, the best. 



In preparing the work I have, of course, drawn largely from many 

 sources, both text-books and works of original research ; for whatever 

 of merit there be in a work of this kind must consist not so much in 

 the novelty of the matter as in the selecting, grouping, and presenta- 

 tion. Such obligations are acknowledged in the pages of the work. 

 I can not forbear, however, making here a special acknowledgment of 

 my indebtedness, in the historical part, to the invaluable Manual of 

 Prof. Dana. I must also acknowledge especial indebtedness to Profs. 

 Marsh, Newberry, and Cope, and the geologists and paleontologists of 

 the United States Surveys, in charge of Prof. Hayden and Lieutenant 

 Wheeler, not only for valuable materials, but also for much personal 

 aid. 



