PERMIAN PERIOD. 367 



3. PERMIAN 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. 



1. American. 

 I. Rocks: kinds and distribution. 



The Permian rocks are confined to the Interior Continental basin, 

 and occur in the portion of it west of the Mississippi, — especially in 

 Kansas, and perhaps other parts of the eastern slope of the Rocky 

 Mountains. They overlie conformably the Carboniferous ; and, as the 

 rocks make one continuous series, it is difficult to determine the limit 

 between the two formations. • 



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 on 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 Tjpper Coal-measures, although they contain a few genera 

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

 Rep. on Nebraska, 1872.) 



II. Life. 



Nothing is yet known respecting the American Permian flora. 

 In the beds admitted by all to be probably Permian, there are only 

 a few Mollusks. 



The species here figured occur in the uppermost beds (Permian of Meek & Hayden). 

 Fig. 887, 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 



