504 



CENOZOIC ERA— AGE OF MAMMALS. 



partly the same locality as the Miocene White River basin, but more 

 extensive, reaching southward in patches almost to the Gulf, and north- 

 ward into British America. 2. In Oregon also there is a Pliocene basin, 

 occupying partly the same region as the previous Miocene. 3. Another 

 discovered by Cope in the basin of the Eio Grande. 4. According to 

 King, the Oregon and Nevada lake-deposit was in Pliocene times greatly 

 extended, so as to cover the whole Basin region, but has been largely 

 removed by erosion or covered by Quaternary deposits. 



All these deposits are imperfectly lithified sand and clays in nearly 

 horizontal position, and many of them have been worn by erosive agen- 

 cies in the most remarkable way, sometimes into knobs and buttes like 

 potato-hills on a large scale, sometimes into castellated and pinnacled 

 forms, which resemble ruined cities. These are the " Mauvaises Terres " 

 or " Bad Lands " of the West (Fig. 843). 



Fig. 843.— Mauvaises Terres, Bad Lands (after Hayden). 



On the Pacific coast, a large portion of the Coast Ranges from 

 Southern California to Washington is Tertiary, as are also in many 

 places the lowest foot-hills of the Sierras. 



Physical Geography. — From what has been said of the distribution 

 of the rocks of this age, it is easy to reconstruct in a general way the 

 physical geography of the American Continent during the early Ter- 

 tiary period. In the northern part the Atlantic shore-line was prob- 

 ably beyond the present line, for there is no Tertiary deposit visible 

 there. The shore-line of that time crossed the present shore-line in 

 New Jersey, then passed along the line of junction of the Tertiary with 

 the Metamorphic, its waves washing primary shores all along the At- 

 lantic coasts, as it does now in the northern portion only ; then along 



