372 PALEOZOIC TIME — CARBONIFEROUS AGE. 



tinuation of the conditions that characterized the Carboniferous 

 period. That era, limestone-making over these western regions, 

 was prolonged into another when the limestones formed still, but 

 with numerous interruptions by clay-depositions ; and these alter- 

 nations were perhaps due to an increasing frequency in the oscilla- 

 tions and shallowness of the waters. 



The beds are continuous with the Carboniferous, without inter- 

 ruption or unconformability, and yet are true Permian, because they 

 belong to the Permian period in geological time, — a fact indicated 

 by the identity of genera, and the close analogy of the species of 

 fossils with the Permian of Europe. 



2. FOREIGN PERMIAN. 

 I. Rocks : kinds and distribution. 



The Permian strata of England occur in view along the borders 

 of the several coal regions, excepting that of South Wales. They 

 occupy a small area in Ireland about the Lough of Belfast. They 

 consist of red sandstone and marls overlaid by magnesian limestone. 

 In Europe the Permian beds in like manner border directly upon 

 the Coal measures, and the rocks are similar in general character 

 to those of England. 



The Permian beds, before their relations were correctly made 

 out, were included, along with part of the Triassic, under the 

 name " New Eed Sandstone/' and also the " Poikilitic group." 



They occur in central Germany from southern Saxony along the Erz Moun- 

 tains, over the small German States, west to Hesse Cassel and north to the Hartz 

 Mountains and Hanover, adjoining. Within this area Mansfeld is one noted 

 locality, situated in Prussian Saxony, not far from Eislehen ; another is on the 

 southwest borders of the Thuringian forest (Thiiringerwald), in Saxe-Gotha, a 

 line which is continued on to the northwest by Eisenach towards Miinden in 

 southern Germany. 



In Russia the Permian formation, according to Murchison, covers a region 

 twice the size of France, extending over the districts that lie along the west side 

 of the Urals, — Vologda, Perm, and Orenburg, — and others more to the west, and 

 thus including the country between the Volga and the Urals. 



In Thuringia and Saxony the subdivisions of the rocks are (1) the red beds 

 (or rothe todte liegende, Red dead layers, — a sandstone so called because the beds 

 are red and contain no copper), overlaid by the copper slates (Kupferschiefer, — 

 a clay-slate worked for its copper at Mansfeld). 2. The magnesian limestone, 

 consisting of (a) Lower Zechstein, a gray, earthy limestone; (b) Upper Zechstein ; 

 (c) Rauchwacke, a shale partly calcareous and concretionary; (d) Stinkstein, 

 an impure, fetid limestone. The limestone in England has four divisions : 



