812 E. O. ULRICH CORRELATIONS OF CHESTER FORMATIONS 



sandstone is regarded by Weller as wanting in Hardin Comity, Illinois, 

 and in Kentucky, where its position is said to be indicated by a supposed 

 unconformity between my Ohara zones 1 and 2. I, on the contrary, have 

 denied this reputed absence of the Aux Yases sandstone and have at- 

 tached little importance to the local break between Ohara zones 1 and 2. 



(3) I recognize a representation of the Upper Ohara (zones 2, 3, and 

 perhaps 4) in the vicinity of Sainte Genevieve, Missouri, and in Union 

 County, Illinois. In the former place this representative underlies the 

 typical Aux Vases sandstone and in the latter place it underlies beds of 

 sandstone and shale that I regard as corresponding to the Aux Vases. 

 Weller, on the contrary, denies the presence of the Upper Ohara in the 

 first of these places beneath the Aux Vases, and prior to 1920 regarded 

 all of the Upper Ohara as corresponding to his Eenault formation, which, 

 like the Yankeetown formation, is typically developed in the Mississippi 

 Valley proper and there overlies the Aux Vases sandstone. In his 

 Hardin County Eeport, however, he places only the cherty top zone 4 of 

 the Ohara on the plane of the Eenault, zones 2 and 3 now being distin- 

 guished as a distinct formation, named Shetlerville limestone, concerning 

 which he is uncertain whether it corresponds to the Aux Yases sandstone 

 or belongs in a hiatus between that sandstone and the overlying Eenault. 



(4) I am inclined to contemporize the lower half of the lower two- 

 thirds of the Okaw limestone of Eandolph County, Illinois, with the 

 Cypress sandstone of southern Illinois and western Kentucky; also, to 

 regard the Golconda shale and the limestone as unrepresented in the 

 Eandolph County section. Weller, on the other hand, correlates the Gol- 

 conda with the greater lower part of the Okaw and the Cypress as passing 

 laterally into a thinner sandstone in Eandolph County, to which he 

 applied the name Euma sandstone. 



Eegarding the fourth of our major differences I shall say little on this 

 occasion beyond the bare statement that I still regard the Middle, and 

 perhaps also the Lower, Okaw as distinct from the Golconda. The evi- 

 dence in this case is mainly negative: the most characteristic of the 

 Golconda fossils have not been fOund in the Okaw limestone, and those 

 of the Okaw have not been observed in the Golconda. The half dozen or 

 more of small mollusks that are common to the two formations are of 

 types that range with so little modification from the Spergen on to the 

 Potts vi lie that I am little inclined to credit their testimony with much 

 value in refined stratigraphic correlations. It is precisely these small 

 pelecypods and gastropods in the Okaw limestone that in 1905 misled me 

 into correlating this limestone with the Gasper limestone of Kentucky, 

 in which very similar, if not precisely the same, species are found. 



