362 GEOLOGY OF NORTHWESTERN TEXAS. 



to the Sub-Carboniferous in the vicinity of Fort Belknap and Crystal Falls, in 

 Young and Stevens counties. He says: "The Brazos Coal Field is the 

 southwestern limit of the Missourian or fourth bituminous coal basin of the 

 United States. The Coal Measures of Stephens and Young counties belong 

 to the Carboniferous age. The coal strata proper are eighty-five feet thick, 

 and are included between an upper sandstone and conglomerate representative 

 of the Millstone Grit, or Pottsville conglomerate No. 12 of the Pennsylvania 

 Series, and a lower gray limestone, representative of the mountain limestone 

 or Chester and St. Louis limestone of the Mississippi Valley." 



That Mr. Ashburner was mistaken in supposing the conglomerate to be the 

 equivalent of the Millstone Grit of the Pittsburg beds and the limestone below 

 it, belonging to the Chester Group, is very readily seen by reference to the 

 general section made from the northeastern part of the Coal Measures to the 

 southeastern part thereof, or from the highest beds to the lowest, passing 

 through Belknap. 



As he finds the Coal Measures in the western edge of Parker County, 

 which is at least one thousand feet below his Chester limestone stratigraphic- 

 ally, and free from any serious faulting, it is useless to give very serious at- 

 tention to his suggestions about the Sub-Carboniferous being in Young and 

 Stevens counties. 



The characteristic fossils of the Coal Measures are very abundant and will 

 be given in another place in this Report; and the most of them were found 

 below the limestone thought by Mr. Ashburner to be Sub Carboniferous. 



The following fossils were found at one locality near Graham, and the 

 stratum from which they were taken is below the limestone thought to be 

 Sub-Carboniferous by Mr. Ashburner: 



Allorisma subcuneata, Meek and H. Spiriferina kenluckensis, Shumard. 



Bellerophon percarinatus, Conrad. Zaphrentis spinulifera, Hall. 



B. carbonarius, Cox. Productus longispinus, Sowerby. 



Euomphalus rugosus, Hall. Hemiphrontes crassus, Meek and Hayden. 



Lophophyllum prohferum, McChesney. Nucula ventricosa, Hall. 

 Pinna per acuta, Shumard. Rhynchonella utaf, Marcou. 



Pleurotomaria sphcerulata, Conrad. Spirifer lineatus, Martin. 



P. tabulata, Hall. Myalina subquadrata, Shumard. 



Productus cor a, d'Orbigny. ChcEtetes milleporaceus, Haines. 



P. costatus, Sowerby. Orthoceras rushensis, McChesney. 



P. nebrascensis, Owen. . Conocardium obliquum, Meek and W. 



Schizodus wheeleri, Swallow. Aviculopecten occidentalism Shumard. 



Spirifer cameratus, Morton. 



Mr. Ralph S. Tarr, after studying that portion of the district lying along 

 the Colorado River, came to the conclusion that there existed a considerable 



