CORRELATION 313 



Parastrophia lenticularis and Ccelospira planoconvexa are associated 

 with Virgiana barrandei in the Anticosti Island region. A form very 

 close to P. lenticularis is also common in the Virgiana zone in Wisconsin, 

 and Ccelospira planoconvexa was reported by Whitfield from a correspond- 

 ing horizon of the Mayville beds near Hartford, Wisconsin. There 

 seems no doubt that the Virgiana zone in the upper part of the Mayville 

 beds in Wisconsin is to be correlated with the zone of Virgiana barrandei 

 in the upper part of the Becsie Eiver formation of Anticosti. 



The lower and middle parts of the Mayville beds, which correspond in 

 time to the Edgewood formation of Illinois and Missouri, occur below the 

 Virgiana zone in Wisconsin, and are thus shown to be older than the 

 corresponding strata containing Virgiana barrandei in the Anticosti 

 region; but they can not be readily correlated with any definite horizon 

 in the Anticosti section. However, from the relation of the strata bearing 

 Edgewood fossils to the Virgiana zone in Wisconsin, the Edgewood for- 

 mation can not be younger than about the middle of the Becsie River 

 division of the Anticosti Island section. 



The Girardeau limestone, which is the oldest of the Alexandrian for- 

 mations in Illinois and Missouri, is not represented in Wisconsin or 

 northeastern Illinois. Its horizon can not be definitely recognized in the 

 Anticosti section, but it probably corresponds in time to the lower part 

 of the Becsie River formation. 



Relation of the Sexton Creek Limestone to the Cataract 



Formation 



In view of the fact that Ccelospira planoconvexa is associated with 

 Virgiana barrandei in the Anticosti region and has been found associated 

 with the variety of this species in the Upper Mayville beds at Hartford, 

 Wisconsin, and that it is a characteristic fossil of the basal (Manitoulin) 

 member of the Cataract 8 formation, it is possible that the Virgiana hori- 

 zon (Upper Mayville beds) of Wisconsin is to be correlated with the 

 basal part of the Manitoulin member of the Cataract formation in 

 Ontario, but it more probably belongs to a time shortly preceding the 

 Cataract. The Manitoulin member not only contains Ccelospira plano- 

 convexa in considerable abundance, but also Eldnopora verrucosa and a 

 number of other species characteristic of horizons near the middle of the 

 Sexton Creek limestone, with which formation the Manitoulin member 

 of the Cataract is probably equivalent in time. It is noteworthy that no 

 shells of Virgiana or of the numerous species of Stricklandinia that are 



8 Charles Schuchert : Medina and Cataract formations of the Siluric of New York and 

 Ontario. Bull. Geol. Soc. Am., vol. 25, no. 3, 1914, pp. 277-320. 



