ie 
JOURNAL OF GEOLOGY 
A Semi-Quarterly Magazine of Geology and 
Related Sciences 
EDITORS 
THOMAS C. CHAMBERLIN, zx General Charge 
ROLLIN D. SALISBURY 
Geographic Geology 
SAMUEL W. WILLISTON 
Vertebrate Paleontology 
STUART WELLER 
Invertebrate Paleontology 
ALBERT JOHANNSEN 
Petrology 
WALLACE W. ATWOOD 
Phystography 
WILLIAM H. EMMONS 
Economic Geology 
ROLLIN T. CHAMBERLIN, Dyxzamic Geology 
ASSOCIATE EDITORS 
SIR ARCHIBALD GEIKIE 
Great Britain 
HEINRICH ROSENBUSCH 
_ Germany 
THEODOR N. TSCHERNYSCHEW 
Russia 
CHARLES BARROIS 
France 
ALBRECHT PENCK 
Germany 
HANS REUSCH 
Norway 
GERARD DE GEER 
Sweden 
ORVILLE A. DERBY 
Brazil 
T. W. EDGEWORTH DAVID 
Australia 
BAILEY WILLIS 
Argentine Republic 
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 
Stanford University 
RICHARD A. F. PENROSE, Jr. 
Philadelphia,. Pa. 
WILLIAM B. CLARK 
Johns Hopkins University 
WILLIAM H. HOBBS 
University of Michigan 
FRANK D. ADAMS 
McGill University 
CHARLES K. LEITH 
University of Wisconsin 
VOLUME XIx 
Dhe Aniversity of Chicago Press 
CHICAGO, ILLINOIS 
