92 C. E. KEYES INTERMONT PLAINS OF THE ARID REGION 



tively thin instead of being of great thickness, as heretofore generally 

 regarded ; 



(7) The central playas, which many of the intermont plains contain, 

 are areas of great eolian degradation as well as of sheetflood aggradation ; 



(8) The main denuding and leveling agent is eolian in character; 



( 9 ) Water action has a very subordinate influence ; 



(10) Sheetflood erosion has a general importance in plain-forming 

 that has long been overlooked ; 



(11) What valley corrasion is in the humid region, planorasion is in 

 the dry regions ; 



(12) Under conditions of an arid climate, a general plain of great ex- 

 tent may be formed without reference to baseleveling ; 



(13) The main significance of a definite rock-fioor to the desert plains 

 is the verity of eolian erosion as the chief factor in the geographic devel- 

 opment of an arid country. 



