AMERICAN DEVONIAN 395 



Superior, where it turns westward to an unknown distance, the 

 covering of newer rocks preventing the tracing of the line in that 

 direction. It reappears in northeastern Iowa, whence it turns 

 eastward across Illinois and then sweeps northward enclosing a 

 great bay which extended across Michigan, Ontario, and central 

 New York nearly to the line of the Hudson, where it encounters 

 the western shore of the Appalachian land. The islands over 

 southern Ohio, Kentucky, and Tennessee made by the Cincinnati 

 uplift at the close of the Ordovician, remained much as they had 

 been during the Silurian. The Missouri island, on the other 

 hand, may have been joined to the Wisconsin peninsula and to 

 the land mass of the Southwest. It has been suggested that a 

 north and south ridge of land extended from Wisconsin all the way 

 to South America, dividing the American seas into eastern, interior, 

 and western, just as Europe had been separated into an open 

 northern and a more or less closed southern sea during the 

 Ordovician and Silurian. This suggestion has not yet been 

 definitely confirmed, but it may represent the truth. In the 

 western region extensive islands continued to exist, and were 

 probably somewhat larger than they had been in the Ordovician. 



A region separate in its geographical development was the 

 northeastern or Acadian province, which included the enlarged 

 Gulf of St. Lawrence and the narrow channels which still ran 

 southward and southwestward across New England and the mari- 

 time provinces of Canada. 



In the northeastern bay of the great Interior Sea the records of 

 the Devonian period begin with the formation of a series of thick 

 sandstones, of which the oldest is the Oriskany, a calcareous 

 sandstone that is rendered porous on weathering by the removal 

 in solution of the calcareous material and of the fossils with which 

 the rock is crowded. The Oriskany is found over the eastern half of 

 New York and southward along the Appalachian range to Virginia. 

 It is also reported from the folded area of northern Alabama, 

 where it overlaps the Cambrian and Ordovician, indicating a trans- 

 gression of the sea over the land in that region, for the Silurian 

 is not represented there. Westward the Oriskany extends into 



