Weno and Pawpaw Formations 17 



limestone level passes between Fort Stockton and Sheffield and eastward to 

 a point near Pecos, thence some distance north of Coke and Runnels coun- 

 ties, north of the Central Mineral Region, and approximately to the north- 

 ern border of Hood County, near Comanche Peak. Here the Edwards out- 

 crop disappears eastward under the later formations. An extended study 

 of the rudistid facies will be necessary to define this boundary line pre- 

 cisely ; but it is cited here as an illustration of the type of lithological vari- 

 ations seen within the extent of the Texas Comanchean outcrops. For the 

 other Washita formations likewise, much field work will be necessary to 

 map even approximately their different lithological facies ; accordingly the 

 following summary of these formations is brief and condensed. 



GRAYSON FORMATION 



Sandstone facie*: 



Unknown. 



Clay facie*: 



Upper half of the Del Rio Clay (approximately the Gryphea mucronata 

 zone, south of the Brazos River). The middle member of the Grayson 

 is a clay as far north as Denton County, Texas. 



Marl facie*: 



Near Bennington, Durant and Bokchito, Oklahoma, Denison, Fink, 

 Gainesville, Denton, Fort Worth, and Burleson, Texas. This is the pre- 

 vailing facies along the outcrop. The eastermost exposure in Central 

 Texas is east of Roanoke, Texas, where the few, insignificant limy seams 

 seen in the Fort Worth region are represented by eleven conspicuous 

 limestone strata. There is little doubt that this formation grows rap- 

 idly more calcareous eastward and southeastward, and that its limestone 

 facies lies in this direction from the outcrop in North-Central Texas and 

 not far from the outcrop. Passing down the Red River valley, however, 

 this does not hold, for the formation is marly in the Tishomingo quadrangle 

 and near Bennington, Oklahoma, where it has essentially the same lithology 

 and fossils as in Tarrant County, Texas. 



WEST TEXAS 



In the Cerro de Muleros section, Bose's subdivision 8 1 consisting of 

 yellow marls containing Schloenbachia sp., Pecten subalpinus (Bose), 

 Exogyra whitneyi Bose, 2 Hemiaster calvini Clark, Protocardia texana 

 (Conrad), and Enallaster bravoensis Bose, is Grayson. It overlies the 

 Mainstreet formation, here a sandstone, and underlies subdivision 9, a 



'Bose: Inst. Geol. Mex. Bol. 25, p. 27-28. 

 2 B6se: Univ. Texas Bull. 1902, p. 10. 



