XX ACKNOWLEDGMENTS 
The Biological Survey, U. 8. Department of Agriculture, 
gave permission to reproduce the map showing the distri- 
bution of the beaver and aspen. 
Vernon Bailey of Washington, presented the beautiful 
photograph of a beaver used as the frontispiece, and gave 
his consent to the use of the cut of the beaver’s hind foot, 
first published in the Journal of Mammalogy, May, 1923. 
Dr. Oliver P. Hay, Associate of the Carnegie Institution 
of Washington, was very helpful in his suggestions concern- 
ing the ancestry of the beaver, and kindly read the manu- 
script of that section of the book. 
David C. Mills, General Director of the National Asso- 
ciation of the Fur Industry, was good enough to have 
prepared and to send me a graph showing the range of 
prices of beaver fur for several years, which was of the ut- 
most aid in preparing my statement of that matter. 
The authorities of Colorado College gave permission to 
photograph the stick cut by beaver and shown in figure 72. 
