38 RAYMOND C. MOORE AND FREDERICK B. PLUMMER 



of rare species which may be considered as satisfactory index fossils 

 are found in both. One very interesting element in the Graham 

 fauna is the group of ammonoids, or, in part, true ammonites, which 

 occurs in the Wayland shale. While a number of these have been 

 found nowhere outside of the Graham, they are very strongly 

 suggestive of the Permian; indeed, so much so that if the associated 

 invertebrate fauna and stratigraphic position were less definitely 

 certain, the containing rocks would probably be regarded as Per- 

 mian. The Graham formation is referred to the Upper Coal 

 Measures and is beHeved to be approximately equivalent in age to 

 the Kansas City formation of the Kansas section. There are 

 marked similarities in the faunas of these horizons, and each is 

 followed by a pronounced change in fauna, marked by the dis- 

 appearance of many of the common elements in the previous 

 invertebrate groups and by the appearance of new forms such as 

 Enteletes hemiplicata, Chonetes granulifer meekianus, and other 

 shells, which became widely distributed and abundant in the 

 closing portion of the Pennsylvanian. The greater thickness of 

 the Graham formation in the north, 500 to 600 feet as compared 

 with 100 feet or less in the south, and its much more clastic char- 

 acter in the north appear to be associated with the uplift of the 

 Arbuckle Mountains in southern Oklahoma which independent 

 studies indicate was subsequent to the time of the deposition of the 

 Wewoka formation and long after the beginning of the Penn- 

 sylvanian. 



The Thrifty formation, named from the town in central Brown 

 County, includes the strata from the sandstone which discon- 

 formably overlies the Graham formation to the top of the limestone 

 which forms a prominent escarpment in the town of Breckenridge, 

 Stephens County. The formation consists of thick shales which 

 are less fossiliferous and brighter in color than those of the Graham, 

 limestones which are thicker and somewhat more massive than 

 those of other divisions of the Cisco, and some sandstone and coal. 

 It has been mapped from Jermyn in Jack County through Young 

 and Stephens counties to the border of the Cretaceous in Eastland 

 County. Inliers belonging to the Thrifty appear in the midst of 

 the Cretaceous near Romney and Bethel, and it has been traced 



