STRATIGRAPHICAL GEOLOGY. 455 



therefore suggested the name of Dyassic as a more suitable 

 general term than Murchison's name derived from the Perm 

 province. He further proposed to associate the Dyas and 

 Trias as members of one great period in the geological 

 succession, equal in rank with the next older Silurian and 

 Devonian or greywacke period, and with the next younger 

 Jurassic and Cretaceous period. H. B. Geinitz (1861-62) 

 adopted Marcou's term of Dyas for the Permian system, and 

 at the present day both names are usually given in the 

 text-books. 



The Dyassic deposits in the Saar and Rhenish district were 

 investigated in detail by E. Weiss (1869-72), who proved 

 the palaeontological identity of the Fish, Amphibian, and 

 Plant remains in the Lebach strata of the Saar basin with the 

 Red Underlyer series in Lower Silesia and Bohemia, and 

 transferred the Cuseler strata below the plant-bearing series 

 from the Carboniferous system with which they had been 

 erroneously included to the Dyassic system. Weiss also 

 pointed out as important features of distinction that the 

 lowest beds of the Red Underlyer or Lower Dyas occasionally 

 contained workable coal-seams, and that the upper beds of 

 the Lower Dyas were interbedded with thick flows of eruptive 

 rocks (porphyry, porphyrite, melaphyre, etc.). Similar features 

 were determined by the geologists of the Prussian Survey 

 Department in the Harz, in Thuringia, and in Silesia, and by 

 Credner and Sterzel in Saxony. 



The structure and composition of the Copper Slate and 

 Zechstein group, or Upper Dyas, had been so exhaustively 

 treated by Lehmann, Fiichsel, and Freiesleben that little 

 remained to be added by recent research. From the 

 predominance of fossil fishes and plant remains in the copper 

 siates, and the frequent intercalation of thick deposits of 

 salt between more calcareous fossiliferous portions of the 

 Zechstein, the Upper Dyas of Central Europe is assumed 

 to have taken origin in large inland seas, occasionally subject 

 to periods of desiccation. 



In the Central French plateau, the development of the 

 Permian rocks is very similar to that in the Saar basin. 

 The English deposits correspond more to the Thuringian 

 development, and consist of the Red Underlyer group (locally 

 called "Lower New Red Sandstones"), bituminous shales, 

 Magnesian limestone, dolomite, marls, and gypsum. An 



