VOLUME XXI li 



THE 



NUMBER 6 



Journal of Geology 



A Semi-Quarterly 



Edited By 



THOMAS C. CHAMBERLIN AND KOLLIN D.SALISBURY 

 With the Active Collaboration of 



SAMUEL W. WILLISTON 



Vertebrate Paleontology 

 STUART WELLER 



Invertebrate Paleontology 



ALBERT JOHANNSEN 



Petrology 

 ROLLIN T. CHAMBERLIN 



Dynamic Geology 



ASSOCIATE EDITORS 



SIR ARCHIBALD GEIKIE, Great Britain 



CHARLES BARROIS, France 



ALBRECHT PENCK, Germany 



HANS REUSCH. Norway 



GERARD DeGEER, Sweden 



ORVILLE A. DERBY, Brazil 



T. \V. EDGEWORTH DAVID, Australia 



BAILEY WILLIS, Argentine Republic 



GROVE K. GILBERT, V\^ashington, D.C. 



CHARLES D. WALCOTT, Smithsonian Institution 



HENRY S. WILLIAMS, Cornell University 

 JOSEPH P.IDDINGS, Washington, D.C. 

 JOHN C. BRANNER, Leland Stanford Junior 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 

 WALLACE W. ATWOOD, Harvard University 

 WILLIAM H. EMMONS, University of Minnesota 



SEPTEMBER-OCTOBER 191 5 



SOME EVENTS IN THE EOGENE HISTORY OF THE PRESENT COASTAL AREA OF 



THE GULF OF MEXICO IN TEXAS AND MEXICO - - E. T. Dumble 481 



THE STRENGTH OF THE EARTH'S CRUST {Concluded). VIII. PHYSICAL CONDITIONS 

 CONTROLLING THE NATURE OF LITHOSPHERE AND ASTHENOSPHERE 

 (Section B) ------ Joseph Barrell 499 



POPOSAURUS GRACILIS, A NEW REPTILE FROM THE TRIASSIC OF WYOMING 



M. G. Mehl 516 



THE CANNONBALL MARINE MEMBER OF THE LANCE FORMATION OF NORTH 

 AND SOUTH DAKOTA AND ITS BEARING ON THE LANCE-LARAMIE PROB- 

 LEM ........ E. Russell Lloyd and C. J. Hares 523 



VARIATIONS OF GLACIERS. XIX ...--. Harry Fielding Reid 548 



A NEW GENUS AND SPECIES OF AMERICAN THEROMORPHA. MYCTEROSAURUS 



LONGICEPS ----------- S. W. WiLLiSTON 554 



USE OF THE SLIDE RULE IN THE COMPUTATION OF ROCK ANALYSES 



James H. Hance 560 



LAKE SUPERIOR HIGHLANDS: THEIR ORIGIN AND AGE - - Charles Keyes 569 



SUMMARIES OF PRE-CAMBRIAN LITERATURE OF NORTH AMERICA FOR 1909, 



1910, 1911, AND PART OF 1912 ------ Edward Steidtmann 575 



THE 



UNIVERSITY OF CHICAGO 



CHICAGO, ILLINOIS, U.S.A. 



PRESS 



Agents 



THE CAMBRIDGE UNIVERSITY PRESS, London and Edinburgh 



KARL W. HIERSEMANN, Leipzig 



THE MARUZEN-KABUSHIKI-KAISHA, Tokyo, Osaka, Kyoto 



