/v n 



THE 



JOURNAL OF GEOLOGY 



A Semi-Quarterly Magazine of Geology and 

 Related Sciences 



Editors 



T. C. CHAMBERLIN, in General Charge 

 R. D. SALISBURY R. A. F. PENROSE, Jr. 



Geographic Geology Economic Geology 



ALBERT JOHANNSEN C. R. VAN HISE 



Petrology Structural Geology 



STUART WELLER W. H. HOLMES 



Paleontologic Geology Anthropic Geology 



S. W. WILLISTON, Vertebrate Paleontology 



Associate Editors 



SIR ARCHIBALD GEIKIE 

 Great Britain 



H. ROSENBUSCH 

 Germany 



CHARLES BARROIS 



France 

 ALBRECHT PENCK 



Germany 



HANS REUSCH 



Norway 

 GERARD DE GEER 



Sweden 



T 



G. K. GILBERT 



Washington, D. C. 



H. S. WILLIAMS 



Cornell University 



C. D. WALCOTT 



U. S. Geological Survey 



J. C. BRANNER 



Stanford University 

 W. B. CLARK 



Johns Hopkins University 

 O. A. DERBY 



Brazil 



W. E. DAVID 



Australia 



VOLUME XIX 



&f)e mnibersiU) of atijicago ^ress 



CHICAGO, ILLINOIS 



