662 NORTH AMERICAN INDEX FOSSILS. 



beds are of lower Pliocenic age and the Paso Rohles of about the 

 age of the ' Merced series. In the Santa Cruz Mountains, the 

 Merced and Santa Clara beds form the higher, and the Purisima 

 beds the lower Pliocenic. 



In northern Alaska, the upper Colville formation of silts con- 

 tains a Pliocenic fauna, and the Horsefly gravels of the Yukon 

 Territory are referred to the same horizon. 



The Pliocenic of the interior of North America, is of continental 

 origin, and includes as Lower Pliocenic, the Upper Ogalalla beds of 

 Nebraska and the Palo Duro beds; and as Middle Pliocenic, the 

 Blanco beds of Texas. The upper Rattlesnake beds of eastern 

 Oregon are also of Pliocenic age. The Lafayette formation 

 (Orange sands) also probably represent a late Pliocenic river 

 deposit of southern and eastern United States, occurring between 

 the Piedmont plateau and the Atlantic, in the upper coastal plain of 

 the Gulf region, the southern Mississippi basin and perhaps in the 

 valleys west of the Appalachians (Chamberlin and Salisbury). 



D. THE PSYCHOZOIC OR QUATERNARY SYSTEMS. 

 XVI. The Pleistocenic System. 



The deposits of this system in North America are largely con- 

 tinental, glacial material predominating. The glacial and inter- 

 glacial stages and substages commonly recognized in North America 

 are :*® 



II. Champlain substage (marine). 

 lo. Glacio-lacustrine substage. 

 9. Wisconsin or fifth glacial stage (sometimes divided into 



later and earlier Wisconsin substages). 

 8. Peorian or fourth interglacial stage. 

 7. lowan or fourth glacial stage. 

 6. Sangamon or third interglacial stage. 

 5. Illinoian or third glacial stage. 



4. Yarmouth (Buchanan) ? or second interglacial stage. 

 3. Kansan or second glacial stage. 

 2. Aftonian or first interglacial stage. 

 I. Sub-Aftonian or Jerseyan, or first glacial stage. 



The marine Champlain beds are found in northeastern New 



*^ Chamberlin and Salisbury, " Geology," Vol. III., p. 383. 



