PENNSYLVANIAN STRATIGRAPHY OF TEXAS s7 



and 1,400 to 1,500 feet in the north. Six formations have been 

 recognized in the Cisco, as indicated in the foregoing table of 

 stratigraphic divisions, in order from the base: Graham, Thrifty, 

 Harpersville, Pueblo, Moran, and Putnam. As a whole, the Cisco 

 group is not more fossiliferous than other parts of the Texas Penn- 

 sylvanian, but some beds, as the upper shale of the Graham forma- 

 tion, are among the most fossiliferous in the mid-continent region. 

 The Graham formation, named from the county seat of Young 

 County, a place already known to science on account of the unusual 

 ammonoids which have been collected there by J. P. Smith^ and 

 others, appears to rest dis conformably upon the Canyon beds. The 

 older or lower members of the Graham are present only in the north, 

 pinching out southward and being overlapped by the younger or 

 higher members. The formation is distinguished from the under- 

 lying beds by its very clastic character and thinner limestones, and 

 from succeeding beds by its prolific and characteristic fauna. The 

 subdivisions of the Brazos Valley include the Finis shale and sand- 

 stone at the base, Jacksboro limestone, Gonzales Creek shale, 

 Bunger limestone, South Bend shale, Gunsight limestone, and Way- 

 land shale. In the Colorado River Valley there are the Bluff Creek 

 shale, Gunsight limestone, and Wayland shale. The limestones 

 are in each case very thin and are not so persistent as the limestones 

 of the Canyon. The Jacksboro and Gunsight are locally charac- 

 terized by an extraordinary abundance of the coral Campophyllum 

 torquium. The shales, especially the Wayland shale, contain very 

 numerous fossils which for the most part are beautifully preserved 

 and weather out readily from the shale. The fossiliferous zone of 

 the Wayland has been traced in some detail from northern Jack 

 County to Brown County, a distance of some 175 miles, and at 

 every point where suitable exposures were found the characteristic 

 fauna was discovered. One locality a mile south of the town of 

 Gunsight, in southern Stephens County, contains the most sur- 

 prising profusion of well-preserved fossils which has come under 

 the observation of the writers. The fauna is very closely related 

 to that of the Wewoka formation in Oklahoma, for not only is a 

 very large proportion of the species common to both, but a number 



^ J. P. Smith, loc. cit. 



