CENOZOIC TIME — TERTIARY. 883 



streamlets, denuding, transporting, making alluvial deposits, and carrying 

 sediments to the seashores ; and the whole surface was well populated, 

 beyond doubt, by Mammals, Birds, and inferior terrestrial life. The moun- 

 tains of the Appalachian System and its bordering regions on the east, 

 west, and south contributed material for the marine Tertiary beds of the 

 Atlantic and Gulf borders; the weakly consolidated beds of the recently 

 made Laramide mountain ranges afforded the same more abundantly for the 

 thick deposits of the vast freshwater lakes about the summit of the Rocky 

 Mountains and over its eastern slopes ; and the Sierra Nevada and other 

 ranges of the western slopes were a source of supply for other lakes and for 

 the marine Tertiary of the Pacific border. But notwithstanding the work 

 of rivers and other agencies, there have not been found, up to 1894, over 

 the eastern half of the continent away from the sea border, any recognizable 

 fossil-bearing, lacustrine Tertiary deposits, excepting over small spots near 

 the center of the state of Vermont. In the western half of the continent, 

 the only fluvial beds recognized as Tertiaiy, by means of fossils, are those 

 of the auriferous gravels of the Sierra Kevada. Nothing of Tertiary origin 

 has yet been identified in or about the basin of Hudson Bay, or those of the 

 Great Lakes, or in limestone caverns of the Mississippi valley and elsewhere, 

 to prove that these basins and caverns were in existence during Tertiary 

 time. They may have existed, but the proof is wanting. 



This work is indebted for the preceding Tertiarj' map of North America to G. D. 

 Harris, who has prepared it from earlier maps and publications, from unpublished records 

 of the U. S. Geological Survey, and to a considerable extent also from his own personal 

 study of the marine Tertiary along the Atlantic and Gulf borders. Further, the subdi- 

 visions of the eastern Tertiary adopted beyond, and the remarks on the distribution of 

 the beds, are partly from his manuscript notes. In addition, he has revised the pages on 

 the Invertebrate paleontology, of the same region ; and part of its illustrations are from 

 his work on the Tertiary Paleontology of Texas. A list of earlier publications and a 

 review of the facts and of the question of equivalency may be found in the U. S. G. 8. 

 Bulletin, No. 83, by W. B. Clarke, on the Correlation of the Eocene Tertiary, 1891, and 

 in the U. 8. G. 8. Bulletin, No. 84, on the Correlation of the Neocene, by William H. Dall 

 and G. D. Harris, 1892. 



Subdivisions. 



The periods of the Tertiary era proposed by Lyell are the basis of the 

 American subdivisions, namely : (1) Eocene, (2) Miocene, (3) Pliocene. 

 To these are added by some, Oligocene, corresponding in age to the Euro- 

 pean Oligocene. Neocene is also sometimes used for the Miocene and 

 Pliocene. 



The marine and lacustrine formations are independent in fossils, and 

 besides are nowhere interstratified, and hence it is not possible to make out 

 their precise equivalents. As regards the lacustrine beds, even the division 

 into periods is based largely on facts from Europe. Moreover, the species 

 of the marine Tertiary of the Atlantic and Pacific borders are almost wholly 



