358 New York State Museum 



New England and the Maritime Provinces of Canada. 

 This disturbance started in the Middle Devonian but con- 

 tinued even to the end of Devonian time. Meanwhile 

 through the later Middle Devonian the Cordilleran sea 

 was spreading eastward bringing in its waters immigrants 

 from Asia by way of Alaska. The Middle and Upper 

 Devonian beds are separated by an erosion interval indi- 

 cating the withdrawal of the sea at the end of Hamilton 

 time. 



During the Upper Devonian the continental seas were 

 gradually withdrawn, first from the southern Mississippi 

 valley area and then from the interior and the Cordilleran 

 areas, until at the end of the Devonian there was a prac- 

 tically complete emergence of North America. Here and 

 there in the Mississippi valley the Upper Devonian over- 

 laps older rocks where the Lower and Middle Devonian 

 are absent. The Tully limestone marking the base of the 

 Upper Devonian is a locally developed limestone in New 

 York State which carries the characteristic brachiopod 

 Hypothyris cuboides (Hypothyridina venustula) occur- 

 ring also in the Cuboides zone in the Rhenish section of 

 Europe. Following the close of the Middle Devonian 

 and at the beginning of the Upper Devonian, parts of 

 Tennessee, Alabama, Kentucky, northeastern Arkansas, 

 Indiana and western Michigan were submerged and re- 

 ceived deposits of black fissile shale that contains a typ- 

 ical Genesee shale fauna. In all the mentioned areas this 

 is followed by the Ohio or Chattanooga shale now gen- 

 erally conceded to be of early Mississippian age. The 

 Genesee in the east is another mass of black shale which 

 increases in thickness from Lake Erie to Pennsylvania. 

 It is a bituminous black shale with few fossils. These 

 black shales are followed by shales largely arenaceous 



