INTRODUCTION 



This report on the fauna of the Pottsville formation of Ohio 

 below the Lower Mercer limestone is a portion of a much more ex- 

 tensive investigation which deals with the entire Pottsville fauna 

 of Ohio, a large portion of which is at present in manuscript form. 

 The field of study is practically new, as up to the present time very 

 little work has been done on the Pottsville fauna of this State, with 

 the exception of a few papers which treat of the Lower Mercer fossils 

 of Flint Ridge and the vicinity. The formation as developed in Ohio 

 includes thirteen fossiliferous horizons, of which six are marine lime- 

 stones, four iron ores which contain marine faunas, and three shale 

 horizons associated with coal beds which contain fresh or brackish 

 water fossils. 



The collections were made chiefly during the summers of 1918 

 and 1919, and the manuscript was prepared during the summer of 

 1920 and the following university year. In most instances large 

 quantities of fossiliferous rock were collected, from which the fossils 

 were later obtained and prepared for use in the laboratory. The 

 collections used in the preparation of this investigation are the prop- 

 erty of the Geological Survey of Ohio, and all types, figured specimens, 

 and other forms of interest have been placed in the Geological museum 

 of The Ohio State University. 



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