PEEFACE vii 



general illustration of my views. I have felt that although I 

 am open to criticism, my views will be more easily understood, 

 and we shall eventually make more rapid progress in arriving 

 at the correct conclusions as to the alterations in the configura- 

 tion of the oceans and continents that actually occurred in 

 the past than if such maps were altogether omitted. 



The immense advance that has been made in the United \ 

 States in the study of zoology has greatly facilitated my work, j 

 And everywhere in America I found willing helpers ready to 

 impart information. My thanks are particularly due in this 

 respect to Prof. H. F. Osborn, Dr. Matthew and Dr. Hornaday 

 of New York, to Prof. Morse and Mr. John Ritchie of Boston, 

 to Dr. Henry B. Bigelow and Mr. T. Barbour of Harvard 

 University, to the late Dr. A. E. Brown and Mr. Witmer Stone 

 of Philadelphia, to Dr. Dall, Dr. T. W. Vaughan, Dr. Stejneger 

 and Miss Richardson of Washington, to the late Prof. Packard 

 of Providence, to Dr. Ortmann of Pittsburg, to Dr. Van Den- 

 burgh of San Francisco and to Dr. Ruthven of Ann Arbor. 

 Several of my European friends also aided me in many ways. 

 Among them particularly the following members of the staff 

 of the British Museum : Dr. Smith Woodward, who was good 

 enough to look through the proofs and to draw my attention 

 to several errors, Dr. Andrews, Dr. Boulenger, Mr. Regan, 

 Mr. Py craft and Mr. B. B. Woodward. Prof. Hull, Dr. Bruce 

 and Dr. Stapf kindly pointed out to me various valuable 

 sources of information. My most grateful acknowledgment, 

 moreover, is due to the guardians of the Great Libraries, with- 

 out whose ready assistance I should never have succeeded in 

 accomplishing this work. The most generous facilities for 

 study were given me by my friends Mr. Lyster of the 

 National Library of Ireland, Mr. Praeger of the Royal Irish 

 Academy Library and Dr. Foord of the Royal Dublin Society's 

 Library. I am indebted, too, for many services to Mr. Kappel, 

 the Librarian of the Linnean Society, to Mr. Jones, Librarian 

 of the Geological Society, Mr. Waterhouse of the Zoological 

 Society of London, and Mr. Hinch of the National Library of 

 Ireland. 



I am under a great obligation to Messrs. Meiklejohn & Son 



