pa a EE Fat 
ae 
THE 
MOOK NAL OF GEOLOGY 
A Semi-Quarterly Magazine of Geology and 
Related Sciences 
Q. 
KX 
EDITED BY 
THOMAS C. CHAMBERLIN AND ROLLIN D. SALISBURY 
With the Active Collaboration of 
STUART WELLER, ALBERT JOHANNSEN, 
Invertebrate Paleontology Petrology 
EDSON S. BASTIN ROLLIN T. CHAMBERLIN, 
Economic Geology Dynamic Geology 
ASSOCIATE EDITORS 
SIR ARCHIBALD GEIKIE, Great Britain JOHN C. BRANNER, Leland Stanford Junior Uni- 
CHARLES BARROIS, France versity 
ALBRECHT PENCK, Germany RICHARD A. F. PENROSE, Jr., Philadelphia, Pa, 
HANS REUSCH, Norway WILLIAM H. HOBBS, University of Michigan 
GERARD DEGEER, Sweden FRANK D. ADAMS, McGill University 
SIR T. W. EDGEWORTH DAVID, Australia CHARLES K. LEITH, University of Wisconsin 
BAILEY WILLIS, Leland Stanford Junior WALLACE W. ATWOOD, Clark University 
University WILLIAM H. EMMONS, University of Minne- 
CHARLES D. WALCOTT, Smithsonian sota 
Institution ARTHUR L. DAY, Carnegie Institution 
VOLUME XxXIx 
JANUARY-DECEMBER, 1921 
THE UNIVERSITY OF CHICAGO PRESS 
CHICAGO, ILLINOIS 
