PENNSYLVANIC-PERMIC PERIOD 563- 



Ouralian (including the Gschellian) of Europe dates from the Hercynian 

 uplift. Prior to this movement the sea had reached its maximum extension in 

 the coalfields of the northern hemisphere. . . . The final exclusion of the 

 sea from the Appalachian trough appears to have occurred soon after the depo- 

 sition of the Ames limestone, near the middle of the Conemaugh. ... It 

 is probable that the Monongahela was never deposited in the southern Appa- 

 lachian region, from portions of which the Conemaugh may also have been 

 absent. 



"In eastern America, where the relations of land and water were but grad- 

 ually altered and the sedimentation was continuous, the passage to the Stephan- 

 ian flora has no line of sharp paleobotanical demarkation." For the same 

 reason "the Stephanian types persist far up into the Dunkard formation. 



"The Stephanian is marked by the great development of Pecopteris, Callip- 

 tericlium, and Odontopteris of the true type. It witnessed the nearly complete 

 disappearance of Alethopteris, Sigillaria, and Lepidodendron. . . . Before 

 its close appear the first representatives of Callipteris, WalcMa, Tceniopteris 

 of the simple type, Pterophyllmn, Zamites, and Plagiozamites, all character- 

 istic of the Permian or later periods." 



In the upper Mississippi valley, and especially in Kansas, Nebraska,. 

 Iowa, Missouri, and Illinois, the deposits of the Missourian are usually of 

 normal marine origin, and here the fossils of this time occur in abun- 

 dance. The term Missourian has been selected for this series in prefer- 

 ence to Coal Measures. As finally denned by Keyes, Missourian embraces 

 all between the Cottonwood at the top of the Kansas section and the "Win- 

 terset of Iowa or the Bethany of Missouri, which represents the base. The 

 writer, however, makes use of the term to include all of the Kansas sec- 

 tion from the base of the Cherokee to the top of the jSTeosho (see table, 

 page 558), preferring thus to extend the meaning of Missourian rather 

 than to coin another new term. 



Thus far no well denned, or, rather, easily discerned, zones have been 

 pointed out. Girty 184 has determined a mass of material, collected at 

 nearly 500 stations in Kansas, and representing 164 species. These are 

 arranged in 46 stratigraphic zones as determined by Adams. The lowest 

 horizon is the Cherokee at the base of the Missourian, and probably ex- 

 tending into the late Pottsvillian. The seven highest zones are generally 

 referred to the Permic or "Permo-Carboniferons." Girty states: "The 

 table shows the evolution of the latest from the earliest faunas in the sec- 

 tion to have been a progression from a brachiopod to a pelecypod facies. 

 . . . It is without marked interruption at any point, so that sub- 

 divisions appropriate for recognition are not clearly apparent." Chonetes 

 mesolobus is restricted to the six basal zones. The following are the 

 more characteristic fossils of the Missourian, restricting the term in this. 



184 Girty: Bull. no. 211, U. S. Geological Survey, 1903. 



