ART. 21 OEDOVICIAN TRILOBITES ULEICH 81 



southwestern corner of Virginia the Maysville is represented only 

 by its lower formation (the Fairview). At Cumberland Gap and 

 to the south in Sequatchie Valley this is succeeded directly by the 

 Sequatchie formation, which is the southern Appalachian marine 

 equivalent of the Richmond. Following the strike northeastward 

 from Cumberland Gap up the Powell Valley the Sequatchie loses 

 in thickness and probably disappears entirely before reaching Big 

 Stone Gap, so that younger Medinan and finally Clinton beds are in 

 contact with the Fairview. 



In the Clinch River Valley belts to the southeast the Richmond 

 is represented by the nonfossiliferous red, probably continental 

 deposit known as the Juniata sandstone. This extends continuously 

 from northeastern Tennessee to central Pennsylvania and thence 

 under cover to western New York, where it is known as the Queens- 

 ton shale or sandstone. In central Pennsylvania and New York 

 the Juniata and Queenston are underlain by the Oswego (" Gray 

 Medina"), sandstone, also mainly a continental deposit, that is 

 believed to correspond in age with the highly fossiliferous McMillan 

 formation of the Cincinnati section. The Brassfield and Whiteoak 

 represent southern marine invasions that reached the Appalachian 

 Valley only south of Virginia and also only in places that had 

 been occupied previously by the Sequatchie. The Tuscarora and 

 the at least partly equivalent Clinch sandstone rest on the Juniata 

 and like it are unfossiliferous and regarded as continental deposits 

 that in their case correspond in age to the fossiliferous Brassfield 

 and Whiteoak formations which occur in belts to the west of Clinch 

 Mountain. No indication of important movements having occurred 

 during the transition from the Lower to the Upper Medina or, in 

 other words, between the Richmond and Alexandria (or "Albion"), 

 epochs has been observed in the Appalachian Valley region between 

 the Adirondacks and central Alabama. 



North Appalachian Valley. — This column pertains mainly to the 

 Ordovician and early Silurian deposits in Newfoundland, Anticosti, 

 and the St. Lawrence and Champlain valleys. The Canadian and 

 Ozarkian formations in this region are not referred to except to 

 state my opinion that zones F, G, and H of the Newfoundland sec- 

 tion are of Upper and perhaps Middle Canadian age and that the 

 Ozarkian is represented at Philipsburg, Quebec, by beds of the Upper 

 and the Lower series. To this I may add the further opinion that 

 the sections in northern Vermont and at Philipsburg, Quebec, do not 

 include deposits of Middle Ozarkian age; and in the latter section 

 only one of the Champlain Valley Beekmantown formations, namely, 

 the Cassin limestone, has been recognized. Regarding the Chazyan 

 64441—29 6 



