6 PREFACE 



Howorth. Acknowledgment of valuable assistance 

 is also due the Carnegie Library of Pittsburgh. 



But the author's deepest obligation is to Dr. 

 Frederic A. Lucas, Director of the American Mu- 

 seum of Natural History, for the generous interest 

 manifested by him during the preparation of the 

 manuscript and its final editing for scientific accu- 

 racy. Without this cooperation dh the part of 

 Dr. Lucas the author would not have ventured to 

 present this volume to the public. 



Pittsburgh, Pennsylvania. 



