430 C. SCHUCHERT PALEOGEOGRAPHY OF NORTH AMERICA 



Yale University, the present writer's efforts have been largely devoted to 

 the paleogeography of North America. Fifty-seven paleogeographic 

 maps have been made and fifty-two are here published, nearly all Amer- 

 ican sources of geologic literature having been ransacked for information. 

 In presenting this work to his collaborators, the writer feels impelled to 

 state that he is fully aware of the imperfection of these maps, but they 

 are now issued for the purpose of furnishing something tangible on which 

 to work. To continue these studies, and thus be enabled to offer later an 

 improved and larger series of maps, is the hope of the writer, who asks 

 the cooperation of all paleontologists and geologists toward this end. 



While the maps were in process of construction the underlying princi- 

 ples thus brought out were frequently discussed with Professor Barrell, of 

 Yale University, and from time to time the maps themselves were labored 

 over with Ulrich and Stanton. At the Baltimore meeting of the Geo- 

 logical Society of America most of the maps were shown, since which 

 time the seas plotted on them have undergone many a surgical operation 

 at the hands of Canadian and American geologists. During April, 1909, 

 a week was profitably spent in Ottawa, where the maps were much im- 

 proved by suggestions made by the geologists Ami, Ells, Dowling, Mc- 

 Connell, Fletcher, Faribault, McGinnis, Keele, and Lowe, while later two 

 weeks were devoted to the same end by the paleontologists of Washing- 

 ton — Ulrich, Stanton, David White, Ivnowlton, Dall, Walcott, Arnold, 

 Yaughan, Kindle, Bassler, and Breger — a day being finally given to them 

 by Clarke at Albany, New York. Berry, of Johns Hopkins, also helped. 

 Much information in regard to the geology of Alaska was obtained of 

 Brooks. For other areas direct assistance was had of Bansome and Men- 

 denhall. 



To all these gentlemen, to Messrs W. H. Twenhofel and J. A. Larsen, 

 and Miss Lucy Peck Bush, of the graduate department of Yale Univer- 

 sity, the writer desires to express his sincere thanks, which are also due 

 to the various geologists who have worked out the geology of the North 

 American continent and whose publications have given valuable aid in 

 the present investigation, though but few of the authors' names are men- 

 tioned in the text. For the benefit of those persons who may not be 

 familiar with this voluminous literature pertaining to the geology of this 

 continent, the following indispensable catalogues are here cited : 



Darton: Catalogue and index of contributions to North American 

 geology, 1732-1891. Bulletin 127, U. S. Geological Survey, 1896. 



Weeks: Bibliography and index of North American geology, paleon- 

 tology, petrolog}-, and mineralogy for 1892-1900. Bulletins 188 and 189, 

 U. S. Geological Survey, 1902. 



