NOTE ON THE ILLUSTRATIONS 



The original drawings, made especially for this book, 

 are by Charles R. Knight and James M. Gleeson, 

 under the direction of Mr. Knight. The fact that the 

 originals of these drawings have been presented to and 

 accepted by the United States National Museum is 

 evidence of their scientific value. Mr. Knight has 

 been commissioned by the Smithsonian Institution, the 

 United States National Museum, and the New York 

 Museum of Natural History, to do their most im- 

 portant pictures of extinct animals. He is the one 

 modern artist who can picture prehistoric animals 

 with artistic charm of presentation as well as with full 

 scientific accuracy. In this instance, the author has 

 personally superintended the artist's work, so that it is 

 as cori'ect in every respect as present knowledge makes 

 possible. Of the minor illustrations, some are by Mr. 

 Bruce Horsfall, an artist attached to the staff of the 

 New York Museum of Natural History, and all have 

 been drawTi with the help of and under the author"'s 

 supervision. 



