Handbook of Paleontology 295 



stone with its characteristic cephalopods, followed by 

 the Trenton limestone, typically exposed at Tren- 

 ton Falls. The limestones are succeeded by the Upper 

 Ordovician (Cincinnatian) shales: the black Utica 

 shales with their characteristic graptolite zones, the 

 sandy shales of the Frankfort and the mud or "lamelli- 

 branch" facies of the Pulaski formation, the last two 

 formations constituting- the Lorraine beds which are 

 capped by the Oswego sandstone. 



We have seen in New York State in the Middle Or- 

 dovician a lateral change in character of sediments 

 from east to west. The limestones of Trenton time in 

 the west are replaced by shales, mudrocks of near- 

 shore origin, in the east, the Canajoharie shales. As 

 the limestone deposition continued in the clear water 

 of the west the muds from Appalachia spread farther 

 and farther westward (Utica shale) covering limestone 

 beds previously deposited. The muds and limestone 

 beds are everywhere conformable and indeed pass into 

 one another (progressive 'overlap). The mud phase 

 was succeeded by a sandy phase (Schenectady beds), 

 the sandy beds beginning at a higher level in the west 

 (Lorraine beds) just as do the black muds, that is, the 

 first mud beds of the east are older than the first mud 

 beds farther west, and the same is true of the sandy 

 beds. The black muds of both the east and west 

 (Canajoharie, Utica) are characterized by graptolites. 

 In the Hudson valley (Levis trough) the entire Cana- 

 dian and Ordovician is represented by shales and sand- 

 stones (the old "Hudson River group") with character- 

 istic graptolite faunas. 



The fossils. Characteristic fossils of the Canadian and 

 Ordovician systems are illustrated in figures 38 to 41. 

 They are as follows : 



