CONTENTS TO VOLUME XXIII vii 



PAGE 



The Strength of the Earth's Crust {Concluded). VIII. Physi- 

 cal 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 Problem. E. Russell Lloyd and C. J. Hares . . . 523 



Variations of Glaciers. XIX. Harry Fielding Reid . . . 548 



A New Genus and Species of American Theromorpha. Myctero- 



saurus 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. V. Edward Steidtmann . 575 



NUMBER VII 



Revision of Pre-Cambrian Classification in Ontario. Willet 



G. MUler and CyrU W. Knight 585 



Metamorphic Studies. Convergence to Mineral Type in Dy- 

 namic Metamorphism. C. K. Leith and W. J. Mead . . . 600 



The Age of the Cretaceous Flora of Southern New York and 



New Englaito. Edward W. Berry 608 



A Critical Study of the Fossil Bird Gallinuloides wyomingensis 



Eastman. R. W. Shufeldt 619 



Ground-Ice Wedges. The Dominant Form of Ground-Ice on the 



North Coast of Alaska. E. De K, Lefiingwell . . . . 635 



Stratigraphy of the Waverly Formations of Central and South- 

 ern Ohio. Part I. Jesse E. Hyde 655 



Recent Publications 683 



NUMBER VIII 



A Revision of the Sequence and Structure of the Pre- 

 Keweenawan Formations of the Eastern Gogebic Iron 

 Range of Michigan. R. C. Allen and L. P. Barrett . . 689 

 Discussion of Correlation. C. K. Leith and R. C. Allen . . 703 

 Pressure as a Factor in the Formation of Rocks and Minerals. 



John Johnston 730 



