STRATIGRAPHICAL GEOLOGY. 449 



two main groups : (i) Older argillaceous and arenaceous grey- 

 wacke; (2) younger calcareous formations. Whereas Murchi- 

 son, Sedgwick, and Dumont had regarded the older greywacke 

 complex as Silurian, Roemer referred it to the Devonian epoch 

 and identified it with the Terrain Ardoisier and the lowest 

 division of the Terrain Anthraxifere of Dumont. The fossili- 

 ferous limestones of the Eifel, Aachen, Bensberg, Elberfeld, 

 and adjacent areas were identified by Roemer with the lower 

 limestone group of the Terrain Anthraxifere, and the lime- 

 stones in Devonshire and Cornwall. He distinguished as an 

 upper member of the group Anthraxifere certain fine shales 

 and greywackes (Lenne shales), between Elberfeld and the 

 Sieg and from Iserlohn to Waldeck, which Murchison had 

 referred to the Silurian. 



The Palaeozoic formations in Nassau, which Murchison and 

 Sedgwick had ascribed to Silurian and Devonian epochs, were 

 afterwards determined by Beyrich and Roemer to be exclusively 

 Devonian. The brothers Guido and Fridolin von Sandberger 

 made a special study of the district, and in 1847 comprised 

 the strata under the term " Rhenish System." They sub- 

 divided the system into three groups a lower complex of 

 greywacke, Taunus shales, and Wissenbach slates; a middle 

 complex of Stringocephalus limestone, dolomite, and Cypridina 

 shales ; an upper complex of Posidonomya shales. The fossils 

 of the Rhenish system were admirably described by the 

 brothers Sandberger in a monograph published from 1850 to 

 1856. 



The works contributed by Dumont and Gosselet on the 

 Palaeozoic rocks in Belgium provided a thorough groundwork 

 of research in that area. Dumont in 1848 sub-divided the 

 Terrain Ardennais into three groups Devillien, Revinien, and 

 Salmien ; similarly, the Terrain Rhe'nan into three groups 

 Gedinnien, Coblentzien, and Ahrien ; and the Terrain Anthrax- 

 ifere above the Terrain Rhenan into three groups Eifelien, 

 Condrusien, and Houiller. Dumont took little trouble to draw 

 a comparison between these sub-divisions which he erected for 

 the Belgian area and the paleeontological groups which had 

 been determined in other countries. He was strongly of 

 opinion that the same fauna never extends over the whole 

 earth, that there had in all epochs been definite geographical 

 kingdoms of plants and animals, and that consequently the 

 fossil contents of rocks could only be used with extreme 



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