INTRODUCTION 



This bulletin deals with the fauna of the Pottsville formation 

 which, as developed in Ohio, includes thirteen fossiliferous horizons: 

 six marine limestones, four iron ores which contain marine faunas, and 

 three shale horizons associated with coal beds which contain fresh or 

 brackish water fossils. The field of study is practically new, as up to 

 the present time very little work has been done on the Pottsville fossils 

 of this State, with the exception of a few papers which treat of the 

 Lower Mercer fauna of Flint Ridge and vicinity. Collections were 

 made from ninety-three localities, and at many of these places fossils 

 from two or more members were obtained. Exclusive of plant and fish 

 remains, two hundred species were identified, among which are a con- 

 siderable number of new forms and fossils of particular interest. 



The collections were made chiefly during the summers of 1918 and 

 1919, and the manuscript was prepared for the most part 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 study in the laboratory. 

 The fossils used in this investigation are the property of the Geological 

 Survey of Ohio, and all types, figured specimens, and forms of unusual 

 interest have been placed in the Geological Museum of The Ohio State 

 University. The portion of this bulletin which deals with the strati- 

 graphy and fauna of the Pottsville formation below the Lower Mercer 

 limestone was submitted in June, 1921, to the faculty of Bryn Mawr 

 College in partial fulfillment of the requirements for the degree of 

 Doctor of Philosophy. 



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