156 J. J. STEVENSON CARBONIFEROUS OP APPALACHIAN BASIN 



well as in Johnson county of Kentucky. Its area, narrow in Pennsyl- 

 vania and northern Ohio, becomes much wider southward. On the east 

 side of the great basin in Maryland and 90 miles from the nearest locality 

 in Pennsylvania where the Cambridge is clearly recognizable, a marine 

 limestone is found certainly not far from the Cambridge horizon, in- 

 dicating continuance of communication with the ocean on that side. 



The Ames limestone is not reported east from the AUeghenies in 

 Pennsylvania, but is distinctly present in Indiana and Somerset of that 

 state, whence it has been followed across Maryland into Barbour county 

 of West Virginia. This limestone is shown farther west in Penns3dvania, 

 wherever its place is exposed, south from the line of Cambria, Clearfield, 

 and Jefferson counties, and it is equally persistent in Ohio, where, as in 

 Pennsylvania, it is the most useful stratigraphical horizon, being midway 

 between the Pittsburg and Upper Preeport coal beds. It is well shown 

 in the central part of the great basin, under the Cowrun anticline, in 

 Washington of Ohio as well as in Pleasants and Wirt of West Virginia; 

 it is present in the southern portion in Wayne and Cabell counties, arid 

 it ma}^ be the Fourth Possiliferous limestone of Kentucky. No borings 

 with diamond drill have been made in the deeper portions of West Vir- 

 ginia and no statement is possible respecting its presence there. It has 

 not been reported along the eastern outcrop south from Barbour county 

 of West Virginia, but at Charleston one finds a limestone, without marine 

 fossils, midway between the Pittsburg and Upper Preeport coal beds and, 

 like the Ames, associated with deep red shale. At all exposures, except 

 that near Charleston, the Ames carries a marine fauna, and at many 

 places on both sides of the basin it rests on fossiliferous shale or, where 

 that is wanting, on the Harlem coal bed. The fauna seems to differ 

 slightly on the opposite sides, some forms characteristic of the Indiana- 

 Illinois field being present on the west side, but wanting on the east side. 

 It may be discovered, when the fauna has been studied thoroughly, that 

 communication was open to the ocean on both sides. It is not improbable, 

 as suggested by Doctor White, that the fossiliferous limestone of the 

 Northern Anthracite field belongs very near the horizon of the Ames. 

 That bed contains many forms obtained from the Conemaugh and in 

 addition several which have not been reported from any other locality 

 within the Appalachian basin; so that there one may have another 

 problem respecting relation to the ocean. 



With the Ames limestone, inroads of the sea practically ceased. Marine 

 conditions unquestionably were repeated, but never for periods long 

 enough for good development of animal invertebrate life. Limestones 



