542 C. SCHUCHERT PALEOGEOGRAPHY OF NORTH AMERICA 



the Mississippian. Though considerable work has been done on these by 

 Hall, Whitfield, and Walcott, they are not at all understood in the light of 

 modern paleontology and stratigraphy. It may be said, however, that 

 these western faunas are not of the same marine province as those of east- 

 ern America. 



Late in the Middle Devonic the Arctic waters again spread southward, 

 introducing a Euro-Asiatic assemblage of life into the Cordilleran sea. 

 At the close of this epoch this fauna spread through the Dakota sea and 

 connected with the Mississippi basin across Michigan, thus distributing the 

 Hypothyris cuboides fauna into New York. Later in the Upper Devonic 

 the Spirifer hungerfordi fauna is general from California to Iowa, and 

 from Bisbee, Arizona, to Montana. To a limited degree it reaches the 

 Mackenzie basin, and late in Upper Devonic time it extends to central 

 New York. There is, however, another faunal element in the eastern 

 region, best known in central New York, which, through many years of 

 persistent collecting by Clarke, has grown to considerable proportions. 

 This is the biota of the Portage, also known as the Intumescens fauna. 

 In the entire western or Dakota sea there is nothing that can be directly 

 compared with the Portage, while the goniatites and bivalves of the latter 

 formation are in perfect agreement with those of western Germany. Not 

 only has this fauna spread through the New Jersey straits, but also the 

 Spirifer disjunctus fauna of the Chemung, both of which have decided 

 Atlantic and European affinities. 



The Portage sea deposited a black shale from New York to southwest- 

 ern Illinois, but its waters did not communicate with the Gulf of Mexico. 

 On the west side of the Cincinnati axis, the peculiar fauna is traceable as 

 far south as Louisville and central Kentucky; farther south the sea ap- 

 pears to have been a practically lifeless one. 



Throughout the Devonic, Appalachia was apparently a low lying land, 

 which, however, was broadly elevated at the close of the Onondaga, as at 

 this time an extensive foreland was added to this positive element. At the 

 beginning of the Hamilton the foreland was largely re-submerged, and if 

 Appalachia was again subjected to movement in this period it was in the 

 southwestern portion, toward the end of Hamilton time, thus cutting off 

 the intercommunication of the Gulf of Mexico with the Mississippian sea. 

 The Acadian positive element, however, was distinctly lifted up, with 

 folding that began late in Onondaga time and persisted throughout the 

 Hamilton and Chemung. It was during this period of elevation that the 

 rivers of this land transported the great masses of muds and sands now 

 piled up in Maryland, eastern Pennsylvania, and New York, having a 

 thickness in places of more than 10,000 feet. Similarly in Gaspe there 



