Handbook of Paleontology 357 



cinnati anticline. In the west the Cordilleran sea occu- 

 pied much of the Great Basin area, probably connecting 

 on the north with the advancing Arctic sea. As Middle 

 Devonian time continued there was an alteration of con- 

 ditions in the northeastern part of the continent bringing 

 about a change in the character of deposits. The land 

 here was elevated resulting in the rejuvenation of the 

 streams which brought into the sea large quantities of 

 mud and silt, (Marcellus black shales, Hamilton shales 

 and flags), checking the deposition of limestone. These 

 deposits are thick in the east, and grow thinner westward. 

 The accumulation of limestone continued in the Missis- 

 sippi valley and even in New York State thin limestone 

 beds occur at intervals in the thick mass of Hamilton 

 shales. The uplift converted the Gaspe area into a 

 coastal lagoon in which swift streams deposited great 

 masses of sand, these continental deposits containing fos- 

 sils of land plants and giving indications of occasional 

 invasions of the sea. The deposits in New Brunswick 

 and Nova Scotia are also sandstones and shales. Part 

 of the Middle Appalachian area that was uplifted at the 

 end of the Lower Devonian was now occupied by an ex- 

 tension of the interior sea (western Maryland and ad- 

 joining parts of Virginia). At the close of the Middle 

 Devonian there was a further shrinking of the seas coin- 

 cident with the further rise of Appalachia and the reju- 

 venated streams continued to build great deltas in the 

 northern part of the Appalachian trough, (as the Asho- 

 kan bluestone delta in New York). The seaways from 

 the North Atlantic through Acadia connecting the inte- 

 rior sea with the St Lawrence trough were forever de- 

 stroyed by the Acadian Disturbance which resulted in the 

 elevation and folding of the Acadian land throughout 



