PERMIAN PERIOD. 367 



3. PEKMIAN PERIOD (15). 



The Permian period, the closing era of the Carboniferous age, was 

 a time of decline for Paleozoic life, and of transition toward a new 

 phase in geological history. 



The term Permian was given by Murchison, De Verneuil, and Key- 

 serling, after the ancient kingdom of Permia, in Russia, which included 

 the existing governments of Perm, Viatka, Kazan, Orenburg, etc., 

 where the formation exists. In America, no division of the Permian 

 period into epochs has been recognized. 



]. American. 

 I. Rocks: kinds and distribution. 



An upper portion of the Carboniferous formation in Pennsylvania 

 and Virginia has been shown by the plants to be Permian (Fontaine 

 and White), and in Illinois and Texas, by the Reptiles and Amphi- 

 bians (Cope). Permian rocks occur in Kansas, and some parts of the 

 Rocky Mountain region, overlying conformably the Carboniferous, and 

 making one continuous series. 



The rocks are limestones, sandstones, red, greenish, and gray marl- 

 ytes or shales, gypsum beds, and conglomerates, among which the lime- 

 stones in some regions predominate. 



In Kansas, they outcrop along the western border of the Carboniferous region, and 

 also in patches to the east of this range. On the map, p. 144, the Permian is dis- 

 tinguished by light dots en a dark ground. The beds occur also about the Black Hills 

 (near lat. 44° N. and long. 104° W.), on the eastern slope of the Big Horn Mountains, 

 and, according to Shumard, in the Guadalupe Mountains in New Mexico. 



The whole thickness made out by Swallow & Hawn is about 820 feet; and 263 feet 

 of this are called by them the Upper Permian, and the rest the Lower. Meek & Hay- 

 den refer the Lower division, with good reason, and also a part of the Upper, to the 

 Upper Coal-measures. The limestones are usually impure, and also magnesian, like 

 most of the limestones of the same region of older date. They are generally rather 

 soft or irregular in structure, and much interlaminated with clayey or arenaceous beds. 

 Some of the layers contain hornstone. In a review of the Nebraska Carboniferous 

 fossils, Meek refers all to the Upper Coal-measures, although they contain a few genera 

 and species that are especially characteristic of the European Permian. (Hayden's 

 Rep. on Nebraska, 1872.) 



H. Life. 



Some of the peculiarly Permian plants of West Virginia are species 



of Callipteris (C. conferta), Alethopteris (A. gigas), Odoutopteris (0. 



obtusiloba), several arborescent Pecopterids, and Conifers of the genus 



Saportsea. 



The species from Kansas here figured occur in the uppermost beds (Meek &Hayden). 

 Fig. 687, Pseudomonotis Hawnii M. & H., cast of the outside of the left valve: 

 687 a, cast of the interior of the right valve of the same. The genus Pseudomonotis 



