TERTIARY MAMMAL HORIZONS. 



PART I. PARALLELS BETWEP:N TERTIARY 



HORIZONS. 



INTRODUCTION. 



This address is designed to reconsider an old subject in the 

 new spirit and methods of modern palaeontology. It does not 

 pretend to cover the whole subject, but rather certain parallels 

 between the mammalian faunae of America and Europe and be- 

 tween the later Tertiary faunae of Europe ; it is introductory to 

 a more exhaustive treatment. 



The work done hitherto in this field of commanding interest 

 and importance serves mainly to pioneer the more exact com- 

 parisons between Europe and America which are now becoming 

 possible. 



I desire to enter an urgent plea for the establishment of 

 uniform divisions of the Tertiaiy and for the international usage 

 of common terms both as to life stages and life forms. As in 

 military disarmament, this result is easier to propose than attain, 

 because each is willing to disarm on his own basis, each is 

 reluctant to part with either the language or perspective be- 

 longing to the historical development of the geology and palae- 

 ontology of his own land. Yet in these matters patriotism and 

 provincialism naturally should have no weight. Palaeontology 

 knows neither the divisions formed by the English channel, the 

 Rhine, nor the Atlantic ; it does not recognize the superiority 

 of an English system, of a French or German system, or of an 

 American system, but like all its sister branches of science in this 

 time of absolute scientific good will it demands an international 

 system. As during the Tertiary period animals migrated freely 

 by land over the entire northern hemisphere, so our ideas and 

 methods must enjoy a free migration and fall beneath the rigid 

 operation of the law of the survival of the fittest. Since anatom- 

 ical, descriptive, taxonomic and geologic terms are mere symbols 

 for the expression of certain facts, ideas, hypotheses and theories, 

 we should all employ the same symbols whatever our national 



