CONEMAUGH FORMATION 225 



Baker stown coal (34). — A very persistent seam, which in some districts 

 is of considerable economic importance, occurs at an interval varying 

 from 90 to 135 feet above the Masontown coal. The thickness of the coal 

 varies from 2 to 5 feet. This seam occupies the stratigraphic position of 

 the Bakerstown coal of Pennsylvania. It is the locally recognized Bar- 

 ton coal, described b3^ that name in the Report on the Geology of Alle- 

 gany County, but apparently not the Barton coal of the Pennsylvania 

 reports. In the Georges Creek basin it is commonly known as the 

 " Three-foot," in the Potomac valley as the " Four-foot," and in the Castle- 

 man valley as the " Honeycomb " seam. 



Saltsburg sandstone (35). — A massive crossbedded sandstone, about 30 

 feet in thickness, occurs above the Bakerstown coal and is separated from 

 it by a variable thickness of shale. This sandstone is evidently the Salts- 

 burg sandstone of Professor Stevenson, so named from its occurrence at 

 Saltsburg, Pennsylvania. 



Crinoidal coal (36). — A thin but very persistent and characteristic coal 

 seam, which has been of the greatest service in correlation, is found at an 

 interval of from 90 to 160 feet above the Bakerstown coal. This seam is 

 the same as the one which has been called the " Crinoidal coal " in the 

 Pennsylvania reports and the " Crinoidal coal " or " Coal 86 " in the Ohio 

 reports. It is possible also that the " Piatt coal " of the Somerset basin 

 may be the same as the " Crinoidal." The coal is well exposed and has 

 been mined for local use at several places in the Castleman basin and 

 in the Lower Youghiogheiry basin near Friends ville, and also at many 

 places in the northern end of the Georges Creek basin, where it attains 

 the thickness of 28 inches, the greatest known in Maryland. One of 

 these old mines near Mount Savage was visited by Lyell in 1842, who 

 described the occurrence of the coal, its position and thickness, and gave 

 a list of fossils found in the overlying shales.* 



Ames or Crinoidal limestone (37). — The Crinoidal coal is overlain by 

 either a limestone or a calcareous shale full of marine fossils. This lime- 

 stone occurs in a position exactly similar, with reference to the overly- 

 ing and underlying strata, to that of the Crinoidal limestone of the Penn- 

 sylvania reports, and to the Ames limestone of the Ohio reports. The 

 fauna, as far as known, is the same as that found in this bed in Ohio 

 and Pennsylvania. In both of these states and in West Virginia the 

 limestone is of very great persistence and has been of the greatest service 

 in the correlation and location of the coals. 



Elklick coal (38). — A very thin and variable coal, which apparently 



* Travels in North America, with Geological Observations on the United States, Canada, and 

 Nova Scotia. 



