ACKNOWLEDGMENTS 



THE author is greatly indebted to Professor G. H. Parker 

 and Professor H. S. Jennings, who read the manuscript and 

 offered many valuable suggestions. He is also indebted 

 to the kind criticisms of Dr. Donald W. Davis, Dr. E. B. 

 Copeland, Dr. Ross C. Whitman, and. others. For the use 

 of some excellent photographs he has to thank Mr. E. R. 

 Warren. Mr. W. P. Hay rendered invaluable service in 

 selecting and advising in regard to illustrations, in addition 

 to the drawings with which he is credited in the text. Many 

 photographs have been secured through the courtesy of the 

 New York Zoological Society and the American Museum 

 of Natural History, New York City. 



