STRATIGRAPHY OP FOSSILIFEROUS MEMBERS 89 



Sphaerodoma brevis (White) 



Sphaerodoma fusiformis (Hall) ? 



Spaerodoma klipparti (Meek) 



Sphaerodoma newberryi (Stevens) 



Spaerodoma primigenia (Conrad) ' 



Sphaerodoma regularis (Cox) 



Sphaerodoma ventricosa (Hall) 



Conularia crustula White 

 Conularia newberryi Winchell ? 



Orthoceras isogramma Meek 



Orthoceras n. sp. 



Orthoceras sp 



Pseudorthoceras knoxense (McChesney) 



Endolobus (Temnocheilus ?) ortoni (Whitfield) 



Metacoceras pottsvillensis n. sp. 



Epphipioceras sp. 



Phillipsia sangamonensis Meek and Worthen 

 Phillipsia trinucleata Herrick 



LOWER MERCER ORE 

 Stratigraphy and Extent 



The Lower Mercer limestone is associated everywhere with an iron 

 ore, known as the Lower Mercer or Little Red Block ore, which either 

 lies directly over the limestone or is separated from it by a few feet of 

 shale. Where the ore is best developed in southern Ohio, it is remark- 

 ably persistent and is present even where the limestone member is 

 wanting. In thickness it measures from 4 to 6 inches with a maximum 

 of 10 inches. 1 In Lawrence County the ore is found directly on the 

 limestone; in Scioto County an interval of a few feet intervenes, while 

 in Jackson County the average distance between the two members is 

 8 feet, with a maximum of 18 feet. In Vinton and Perry counties they 

 are again in contact. Northward in Muskingum and Licking counties 

 the Lower Mercer ore is present only locally in a few places and is 

 separated from the underlying limestone by about one foot of shale. 2 

 Elsewhere in central and -northeastern Ohio the member is less well 

 represented. Formerly this ore was mined extensively for use in the 

 charcoal furnaces of Scioto, Lawrence, and Jackson counties. 



Although the Lower Mercer ore contains fossils, they are not 

 abundant and represent the same forms as are present in the limestone 

 member. In general, they are smaller showing the effects of impover- 

 ished living conditions which existed in the Pottsville sea during the 

 period of iron ore deposition. 



'Stout, W., Geol. Surv. Ohio, Fourth Ser., Bull. 20, pp. 142, 297, 570, 1916. 

 2 Stout, W., Geol. Surv. Ohio, Fourth Ser., Bull. 21, p. 60, 1918. 



