352 T. E. SAVAGE ALEXANDRIAN SERIES US MISSOURI AND ILLI> 



order to provide a place for the earliest Silurian strata occurring in Illi- 

 nois and eastern Missouri which occupy a position above the top of the 

 generally accepted Cincinnatian (Richmond) and below the Brassfield 

 (Ohio Clinton) limestone. 



Regarding the stratigraphic position of the Brassfield. Professoi Schu- 

 chert 3 states in his classic work on the Paleogeography of Xorth America 

 that "in the Anticosti section it is seen that this so-called Clinton ( Ohio 

 Clinton) or Tripkcia ortoni zone is older than the true Clinton of the 

 Appalachian region." It is now also known that the fauna of the Brass- 

 field limestone is very closely allied to that of the earlier Silurian strata 

 of Illinois and eastern Missouri, as shown in the similarity of several of 

 the genera and species to those of the older Edgewood limestone. For 

 this reason the strata representing the Brassfield in Illinois and Missouri 

 are here included in the Alexandrian series. 



As thus defined the Alexandrian series embraces all of the strata in 

 this region between the top of the Cincinnatian (Richmond) and the top 

 of the Brassfield limestone. It includes strata that have been referred to 

 in the literature under various formation names, as the Girardeau lime- 

 stone. Bowling Green limestone. Xoix oolite, Edgewood limestone. Sexton 

 Creek limestone. Channahon limestone, and Esses limestone. Some of' 

 these strata have been assigned to positions in the geological column as 

 widely separated as the Trenton division of the Ordovician and the Onon- 

 daga of the Devonian system. 



In IS 57 Billings proposed the name Middle Silurian — "•'Anticosti 

 group" * — for the succession of strata exposed on the island of Antic 

 in the Gulf of Saint Lawrence. In the lower part of his Anticosti group 

 Billings included the representatives of Ordovician strata to which the 

 name Richmond has since been applied. In the upper part were included 

 strata equivalent to the entire Xiagaran series of the Xew York section, 

 and in the middle portion were strata belonging to the interval between 

 the Richmond below and the Xiagaran (Xew York Clinton) above, to 

 which has been given the name Alexandrian series. Since the Anti 

 group, as defined by Billings, embraced at the base such an important 

 part of the Cincinnatian series as the Richmond and in the upper part 

 the whole of the Xiagaran series, this term is not considered appropriate 

 or in any sense to have priority as a name for only that portion of the 

 Anticosti section belonging to the interval between the Richmond of the 





3 Charles Schuchert : raleogeography of North America. Bull. Geol. S<»c. Am., to!. 20. 

 pp. 427-606. 



4 E. Billings: Geological Survey of Canada. Report of Progress. 1S57. pp. 247-255 



