206 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



in the western area, in the Beaver foot Trough, the Ordovician (Cana- 

 dian) Glenogle formation is made up of argillaceous and arenaceous 

 shales formed of muds and fine sands derived from a western land 

 area that was probably more elevated than during Upper Cambrian 

 and Ozarkian time. 



The Silurian and Devonian rocks are nearly all calcareous, with 

 some very fine argillaceous and arenaceous matter intermingled and 

 an occasional siliceous, cherty band of limestone. A few bands of fine 

 quartzitic sandstones indicate local changes of land conditions and 

 drainage with a temporary supply of fine sand that was tisually 

 thoroughly washed prior to its final deposition. 



The origin and character of the sediments deposited in the Cordil- 

 leran Geosyncline in Paleozoic time form a most interesting subject 

 for study ; a study worthy of a well-trained young geologist who 

 wishes to make a contribution to the geological history of the western 

 side of the North American continent. 



i 



