636 NORTH AMERICAN INDEX FOSSILS. 



In eastern Illinois and Indiana, the St. Louis limestone proper 

 is preceded by the Salem limestone also known as the Bedford 

 Oolite or Spergen limestone. 



In Indiana, the Black New Albany shale of late Devonic (or 

 early Mississippic) age is succeeded by the Rockford Goniatite 

 limestone and the shales and sandstones of the Knobstone group. 

 This represents Osagean and lower divisions. Above the knob- 

 stone is the Harrodsbiirg limestone, the Bedford Oolite and the 

 Mitchell limestone the latter of St. Louis age. Above this occur 

 sandstones and limestones of Chester age. 



Southeastward, in western Kentucky and western Tennessee, the 

 upper part of the Knobstone constitutes the Tullahoma formation 

 and rests with a basal black shale, probably of lower Waverly age, 

 on earlier Palaeozoic strata. 



In Ohio, the lower Mississippic is mostly represented by sands 

 and shales with some conglomerates, and constitutes the Waverly 

 series or Waverly an. It is in places disconformably succeeded by 

 the Maxville limestone of upper Mississippic age. The Waverly 

 series admits of the following subdivisions : 



6. Logan sandstone. 



5. Black Hand formation. 



4. Cuyahoga shale. 



3. Sunbury shale. 



2. Berea grit. 



I. Bedford shale. 



These units are mostly very variable and of somewhat different 

 values in different regions. In Michigan, the base of the series is 

 formed by the Richmondville sandstone, probably combined Bed- 

 ford-Berea. This rests disconformably on the Antrim black shale 

 and is succeeded by the Coldwater shales, the equivalent of the 

 Cuyahoga shales of Ohio. Above this comes the Marshall sand- 

 stone — in part representing the Logan and then, after a hiatus and 

 disconformity, the Grand Rapids series of limestones and dolomites 

 with gypsum. These latter are of Chester, or perhaps in part 

 of St. Louis age. Above this the coal measure sandstone lies 

 disconformably. 



In western Pennsylvania, the Mississippic series comprises the 

 following divisions : 



