MIDDLE AND UPPEE OEDOVICIAN. 167 



Foerste ^'^ gives the history of the classification of the Cincinnatian series and 

 describes its representatives in the Tennessee Valley and thence south to the central 

 basin of Tennessee. He concludes with the following list of local formations: 



According to the preceding observations, the Ordovician exposures in the valleys of the 

 Tennessee River, the Buffalo River, Swan Creek, and South Harpeth Creek suggest the following 

 lithologic succession, in descending order: 



Cincinnati group: 

 Eiclunond: 



Mannie shale. 

 Leipers creek limestone. 

 Lorraine: 



Warren limestone; clay rock at Newsom. 



Swan Creek limestone. Richly fossiliferous Lorraine limestone in the eastern part of the area 

 studied, containing Platystrophia lynx. 

 Utica: Saltillo limestone. 



The Lorraine appears to become thinner west of the Cincinnati anticline, so as to be repre- 

 sented by thinner sections or so as to be entirely absent along the Mississippi in Missouri and 

 adjacent Illinois, in the Wells Creek basin in northern Tennessee, and along the Tennessee 

 River in southern Tennessee. The Richmond also appears to become thinner west of the 

 northern half of the Cincirmati anticline. It becomes thinner also southward along the flanks 

 of the anticline. In some parts of Tennessee it is entirely absent along the western flank of 

 the anticline. West of the southern half of the anticline, in Tennessee, the thickness of the 

 Richmond appears to vary irregularly. 



Details of the distribution of the Ordovician strata, with numerous graphic 

 sections, are given by Foerste ^^^' ^*° in subsequent articles. 



