4 OSBORN. 



sympathies. For my own part if an approximate synchronism 

 can ever be estabHshed, I would go so far as to advocate the 

 adoption of the standard European divisions for the American 

 Tertiary as soon as the European stages and periods are finally 

 determined upon. In the meantime no one can oppose the im- 

 mediate adoption of the fundamental principle that the old and 

 new world palaeontology should be studied as a unit. 



If we are eager to solve the great number and variety of most 

 interesting questions still unsolved as to the source, origin, filia- 

 tion, migration and extinction of the noble races of animals which 

 passed across the stage of the Northern Hemisphere or Ancient 

 Holarctic Region, during the Tertiary we must hasten to use 

 more exact methods, to agree upon the synchronism of the 

 Tertiary and the arbitraiy limits which we shall assign to the 

 Eocene, Oligocene, Miocene, Pliocene and Pleistocene periods 

 and their subdivisions. The synchronism is a difficult subject, 

 in fact it involves the main question ; the limits of the periods are 

 largely arbitrary and are capable of being settled at once. Al- 

 though the loiver Tertiary of America from the base of the Eo- 

 cene to the summit of the Oligocene is infinitely more complete, 

 in fact an unbroken historic chapter, it will probably prove 

 best that the beautiful series of Tertiary horizons of France 

 should be adopted as the basis of division, partly because of 

 their priority and completeness throughout, but chiefly because 

 of the remarkable alternation of marine and freshwater deposits, 

 whereby the vertebrate is checked by the invertebrate time scale. 

 After we pass the summit of the Oligocene our country affords 

 a series of vistas only while Europe offers a commanding view 

 of the later Tertiary life periods. If France furnishes the initial 

 basis, comparison with America will serve to check and am- 

 plify^thus the final basis for the division of the Tertiary will 

 be comparative. 



European Correlations : — In P^ ranee Gervais, Gaudry, Fil- 

 HOL, Lemoine, Deperet, Boule, and others have drawn the 

 demarcations of the t}^pical horizons. The parallels with Eng- 

 land have been especially set forth by Prestwich and Daw- 

 kins and with Germany by Schlosser, Deperet and v. Zittel, 



