6i4 NORTH AMERICAN INDEX FOSSILS. 



beds are separated by a disconformity. The Lower Ordovicic or 

 Beekmantomn, formerly known as the Calciferous, is subdivided 

 into five divisions lettered from the base up from A to E. 

 Divisions D to E are also called the Cassin limestone. In the 

 Mohawk valley, the lower beds, which rest directly upon the 

 gneiss, are known as the Little Falls dolomite; and in the Black 

 River and northern Adirondack region as the Theresa formation. 

 In the Hudson valley, a part of the Hiidso-n River shales contains 

 the Graptolite fauna of the Lower Ordovicic. These are known as 

 the Deepkill shales, their northeastward extension constituting the 

 Upper Point Levis beds in Quebec, and the St. Anne beds of 

 Newfoundland. 



The Chazy is divided into three divisions (A-C) in the 

 Champlain valley, while northeastward, the Mingen limestones 

 represent the upper Chazy and Black River horizons. Divisions 

 K to P of the Quebec group of Newfoundland approximately 

 represent the northeastern continuation of the Chazy series. The 

 lower divisions are Beekmantownian and Cambric. In the Ottawa 

 River region, the upper Chazy {Camarotoechia plena beds) is 

 known as the Grenville limestone. In the Black River region the 

 Pamelia and Lowville (Birdseye) limestones represent local phases 

 of the upper Chazy. 



The Black River limestone forms the transition to the upper 

 Ordovicic. In the Hudson valley it is represented by the Nor- 

 ma>ns Kill shales carrying graptolites. 



The Utica and Trenton replace each other to a greater or less 

 extent. The Queenston shale is unfossiliferous and believed to be 

 of continental origin. In the southern Appalachians the Ordovicic 

 section comprises the following divisions : 



SUPERFORMATION. 



Basal Siluric (Tuscarora sandstone). 

 Upper Ordovicic (Trentonian). 



Juniata shale and sandstone (continental). 



Bald Mountain conglomerate (Tyrone conglomerate) 



(continental). 

 Eden sandstone. 



Utica shale, generally with some Trenton limestone at the 

 base. 



