THE 



JOURNAL OF GEOLOGY 



A Semi-Quarterly Magazine of Geology and 

 Related Sciences 



EDITED BY 



THOMAS C. CHAMBERLIN AND ROLLIN D. SALISBURY 



With the Active Collaboration of 



SAMUEL W. WILLISTON ALBERT JOHANNSEN 



Vertebrate Paleontology Petrology 



STUART WELLER ROLLIN T. CHAMBERLIN 



Invertebrate Paleontology Dynamic Geology 



ALBERT D. BROKAW, Economic Geology 



ASSOCIATE EDITORS 



SIR ARCHIBALD GEIKIE, Great Britain 



CHARLES BARROIS, France 



ALBRECHT PENCK, Germany 



HANS REUSCH, Norway 



GERARD DeGEER, Sweden 



T. W. EDGEWORTH DAVID, Australia 



BAILEY WILLIS, Leland Stanford Junior 



University 

 GROVE K. GILBERT, Washington, D.C. 

 CHARLES D. WALCOTT, Smithsonian 



Institution 



HENRY S. WILLIAMS, Cornell University 

 JOSEPH P. IDDINGS, Washington, D.C. 

 JOHN C. BRANNER, Leland Stanford University 

 RICHARD A. F. PENROSE, Jr., Philadelphia, Pa. 

 WILLIAM H. HOBBS, University of Michigan 

 FRANK D. ADAMS, McGill University 

 CHARLES K. LEITH, University of Wisconsin 

 WALLACE W. ATWOOD, Harvard University 

 WILLIAM H. EMMONS, University of Minnesota 

 ARTHUR L. DAY, Carnegie Institution 



VOLUME XXV 

 JANUARY-DECEMBER, 191 7 



THE UNIVERSITY OF CHICAGO PRESS 

 CHICAGO, ILLINOIS 



