WEST VIRGINIA GEOLOGICAL SURVEY. 617 



exist in adjoining areas in the measures which outcrop in Gil- 

 mer County. Hence, the following report applies to that 

 county only on the ground that the buried fossiliferous hori- 

 zons may be expected to contain much the same faunas as 

 those in the corresponding strata of Lewis County. 



As may be seen from the register of localities, several col- 

 lections obtained from the Ames and Orlando Limestones 

 have not been studied. The fossils contained in the lists in 

 this report are to be described and illustrated in a forthcoming 

 report on an adjoining area, and it is expected that the re- 

 maining collections from Lewis and Gilmer Counties will be 

 studied and included in that report. In view of the partial 

 nature of the study of the limestones above mentioned, the x 

 differences between the various faunas are somewhat exag- 

 gerated and rare species appear to be restricted to one or the 

 other fauna in some cases probably only because a largi.* 

 enough number of collections has not been examined to re- 

 veal the true distribution of the shells. It is only after ex- 

 tended and intensive study of the faunas of strata so nearly 

 related in time in the Pennsylvanian System as are those in- 

 cluded in the confines of a single series of rocks that differ- 

 ences are to be found which will definitely distinguish one 

 faunule from another. In many instances differences in faunal 

 content accompanying changes in lithologic phase within a 

 formation are as striking as the differences between the fau- 

 nas of two succeeding fossiliferous horizons. Changes in the 

 character of Conemaugh faunas between areas somewhat re- 

 moved from each other are likewise perhaps as noticeable as 

 those between the different faunas in a single section. 



Most of the localities from which fossils were collected 

 fci this report were discovered by D. B. Reger and some col- 

 lections were made by him alone or in company with the 

 writer. 



The accompanying map, Figure 12, shows the progress 

 of the work of describing and illustrating the Pennsylvanian 

 invertebrate fossils of West Virginia to the date of writing. 



