I 65 ] 



IX. On the inapplicability of the new term " Dyas " to the " Per- 

 mian" Group of Rocks, as proposed by Dr. Geinitz. By Sir 

 Roderick Impey Murchison, F.R.S., D.C.L., LL.D. fyc, 



Director-General of the Geological Survey of Britain*. 



1 N the year 1859 M. Marcou proposed to substitute the word "Dyas" 

 ■*■ for " Permian," and summed up his views by saying that he re- 

 garded " the 2sew Red Sandstone, comprising the Dyas and Trias, 

 as a great geologic period, equal in time and space to the Palaeozoic 

 epoch of the Gray wacke (Silurian and Devonian), the Carboniferous 

 (Mountain-limestone and Coal), the Mesozoic (Jurassic and Creta- 

 ceous), the Tertiary (Eocene, Miocene, and Pliocene), and the recent 

 deposits (Quaternary and later) " ! ! f . 



As that author, who had not been in Russia, criticized the labours 

 and inductions of my associates de Yerneuil and von Keyserling, and 

 myself, in having proposed the word " Permian " for tracts in which 

 he surmised that we had commingled with our Permian deposits 

 much red rock of the age of the Trias, I briefly defended the views 

 I had further sustained by personal examination of the rocks of 

 Permian age in various other countries of Europe?. 



It was, indeed, evident that M. Marcou's proposed union of the so- 

 called Dyas and Trias in one natural group could not for a moment 

 be maintained, since there is no conclusion on which geologists and 

 palaeontologists are more agreed, than that the series composed of 

 Roth-liegende, Kupfer-Schiefer, Zechstein, &c, forms the uppermost 

 Palaeozoic group, and is entirely distinct in all its fossils, animal and 

 vegetable, from the overlying Trias, which forms the true base of 

 the Mesozoic or Secondary rocks. 



Owing to such a manifest confusion respecting the true palaeonto- 

 logical value of the proposed " Dyas," we should probably never have 

 heard more of the word, had not my distinguished friend, Dr. Geinitz 

 of Dresden, recently issued the first volume of his valuable palae- 

 ontological work, entitled ' Dyas, oder die Zechstein-Eormation und 

 das Rothliegende ' §. In borrowing the term " Dyas " from Marcou, 

 Dr. Geinitz shows, however, that that author had been entirely 

 mistaken in grouping the deposits so named with the Trias or the 

 Lower Secondary rocks, and necessarily agrees with me in con- 

 sidering the group to be of Palaeozoic age. 



As there is no one of my younger cotemporaries for whom I have 

 a greater respect as a man of science, or more regard as a friend, 

 than Dr. Geinitz, it is painful, in vindicating the propriety and use- 

 fulness of the word " Permian," to be under the necessity of point- 

 ing out the misuse and inapplicability of the word " Dyas." 



* Communicated by the Author. 



t See " Dyas et Trias de Marcou," Bibliotheque Universelle de Geneve, 1859. 



% See ' American Journal of Science and Arts,' 2nd ser. vol. xxviii. p. 256,— 

 the work of M. Marcou having attracted more attention in America than in 

 England. 



§ Leipzig, 18G1. 



Phil. Mag. S. 4. Vol. 23. No. 151. Jan. 1862. V 



