September-October 1923 Vol. XXXI, No. 6 



The Journal of Geolo 



GYl 



Edited By 

 thomas c. chamberlin 



With the Active Collaboration of 



ROLLIN T. CHAMBERLIN, Managing Editor 

 Dynamic Geology 

 STUART WELLER ALBERT JOHANNSEN 



Invertebrate Paleontology Petrology 



EDSON S. BASTIN J HARLEN BRETZ 



Economic Geology Stratigiaphic Geology 



I 



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