INTRODUCTION 43 



parison, to establish so far as possible the homotaxis or the synchronism 

 of the geological subdivisions of the Ca^nozoic in the New and Old Worlds, 

 and to agree upon the limits which shall be assigned to the Eocene, Oligo- 

 cene, Miocene, Pliocene, and Pleistocene Epochs and their stages. 



It will certainly prove best that the grandly successive series of Ter- 

 tiary horizons in France should be adopted as the chief bases of time divi- 

 sion, partly because of their priority of description and definition, but 

 chiefly because in France, owing to the instability of the continent above 

 referred to, there is a remarkable alternation of fresh-water deposits con- 

 taining remains of mammals and of marine deposits containing fossilized 

 shells, the shells serving as time-keepers of the evolution going on in other 

 parts of the world. Thus in France the evolution of mammals, or the 

 vertebrate time scale, is checked off by the invertebrate time scale. As 

 we shall see, the Lower Canozoic of America from the base of the Eocene 

 to the summit of the Oligocene offers us a much more complete life story 

 than that of France; in fact, it is an unbroken historic chapter. The same 

 is true of our Oligocene and to a somewhat less extent of our ]\Iiocene. 

 But the mammal-bearing series is entirely fresh-water. Only during the 

 late Miocene and Pliocene of Florida and in the little known Oligocene of 

 New Jersey, do we discover an alternation of marine and fresh-water con- 

 ditions such as occurs throughout the entire Csenozoic in France. In the 

 Pliocene our country affords only a series of vistas of what was happening, 

 while Europe offers a more commanding view. 



If, therefore, France, Germany, Switzerland, and Italy furnish the ini- 

 tial basis for time standards, comparison with America will serve to check 

 and amplify. Thus the final basis for time divisions of the Csenozoic will 

 be international. There is every reason for the international usage of similar 

 terms, both as to life forms and as to time stages. In these matters 

 patriotism and provincialism naturally should have no weight; palaeon- 

 tology knows nothing of the divisions formed by the English Channel, the 

 Rhine, nor the Atlantic; it does not recognize the superiority of an Eng- 

 lish system, a French, a German, or an American system, but like all its 

 sister branches of science, in these times of absolute scientific good will, 

 demands an international system. If approximate synchronism in the 

 Epochs and Stages can be established, and the present volume is designed 

 to Ijring together all the facts that can be assembled toward such syn- 

 chronism, it will be very desirable to adopt uniform descriptive terms for 

 the European and American geologic divisions. 



Our first object is to show how far the Epochs or Sijstemes of America 

 and Europe can be synchronized and similar permanent limits be placed 

 between them; our second object is to establish Stages as convenient 

 divisions of each, in addition to the descriptive terms Upper, Middle, 

 Loicer, and Basal, which are respectively marked off in the natural geo- 

 logic })oun(laries of the two continents. Of course the synchronizing of 

 the stages and substages throughout will present grc^atcr difficulties and 



