PERMIAN PERIOD. 



373 



(a) compact; (b) fossiliferous ; (c) brecciated; and (d) crystalline and other 

 limestones. 



In Russia there are magnesian limestones interlaminated with sandstones, 

 and marls of various colors, with some gypsum, and an occasional thin seam of 

 coal. 



The coincidence is worth noting that the Permian rocks of Russia or interior 

 Europe lie between its great river the Volga and the summit of the Ural Moun- 

 tains, just as in interior North America they occur between its great river the 

 Mississippi and the Rocky Mountain summits. It may be that on both conti- 

 nents the region between the great river and the ocean had been raised above 

 the sea during the preceding changes. 



II. Life. 



1. Plants. 

 The Permian plants are closely related to those of the Upper 

 Coal measures. They are mostly of the same genera, and in part 

 of the same species. There are Calamites and Equiseta, many ferns, 

 including tree-ferns, and a number of Conifers : yet the prevalence 

 of some new kinds gives a somewhat different aspect to the flora. 

 Among the trees those of the genus Walchia (fig. 616 C) are most 

 characteristic. 



The Ferns are of the genera Neuropteris, Sphenopteris, Peccpteris, etc., and 

 there are also species of Asterophyllites and Annularia, as well as Calamites, 



Fig. 616. 



Figs. 616 A, A', Neuropteris Loschii ; 



616 B, B', Annularia carinata; 616 C, Walchia pini- 

 formis. 



Coal Measure genera. On the other hand, there are no Sigillarise. The Conifers 

 are more varied : they include Arauearites {Dadoxylon), Pinites, Walchia, ate. 



