U. S. GEOLOGICAL SURVEY 
BULLETIN NO. 338 PL 
A EROSION FORMS OF THE LATEST TRACHYTE, SWETT 
HILLS. 
B. EROSION FORMS OF LACCOLITHIC ANDESITE 
THE THREE PEAKS. 
C. CONCRETIONARY EROSION OF THE LACCO- 
LITHIC ANDESITE. THE THREE PEAKS 
