418 Forty-second Report on the State Museum. 



interesting because they show the insensible passage from Devonian to 

 Silurian, are the limestones of Erbray.the Hercynian limestones of the 

 Hartz, the etage G of Bohemia, the Upper Helderberg, the limestone 

 of the Carinthian Alps, of the Urals, etc." (p. 325). " The Coblenzian 

 does not form the base of the Devonian, as frequently asserted by too 

 many authors accustomed to consider the Rhine as the classical 

 region. This Coblenzian etage, like that directly below" (Gedinnian) 

 " also presents two distinct facies in the west of Europe; one arenaceous- 

 schistose (greywackes of the Meuse and Rhine), the other calcareous 

 (the beds of Nehou in Brittany, in the Pyrenees and the Asturias). 

 These Coblenzian limestones, like the Eifelian limestones overlying, 

 (Greifenstein, Porsguen) have a faune propre, which in France we 

 know wel), from the labors of M. Oehlert. These species characteriz- 

 ing the calcareous CobleDzian, are associated with others occurring 

 in the greywacke of the Meuse and of the Rhine, as well as some 

 Bohemian Silurian forms " (p. 325). From an analysis of the calcare- 

 ous Coblenzian fauna, Professor Barrois arrives at the conclusion that 

 it is distinct both from the Hercynian and the Eifelian, younger than 

 the former, older than the latter, and that therefore the fauna of the 

 Erbray limestones, equivalent to the Hercynian and the etage G, the 

 Oriskany and Upper Helderberg (in part), represents the calcareous 

 facies of the Gedinnian, or an earliest Devonian pelagic fauna. 



It will be observed that while this expression in regard to the age of 

 the Hercynian is in harmony with Kayser's first conception, it does not 

 agree with his original suggestions of equivalence with the Coblenzian, 

 nor with his later views in regard to its age. 



The oscillations of the Hercynian ideas, have, in fine, been essentially 

 these: A. Rozmer (1843) regarded the fauna in its typical (Hartz) 

 development, as Upper-Silurian; subsequently the Cephalopod facies 

 and Brachipod facies thereof as representing distinct faunas, the 

 former Devonian, the latter Silurian; Beyrich (1867) believed the two 

 faunas of Roimer, one, and suggested their equivalence to the Bohe- 

 mian F, G, H, and their relation to the Devonian; Kayser (1878) 

 demonstrated their unity and Devonian character and regarded them 

 as the lowest beds of the Devonian, representing a calcareous facies 

 of the Coblenzian fauna of the Rhine, and paralleled with them 

 the Bohemian F, G, H fauna taken in its entirety; in 1880 he 

 regarded them as a lower (not lowest) Devonian fauna, but still a calca- 

 reous facies of the Coblenzian; in 1884 he appears to have resumed 

 his original position in regard to the age of the Hercynian, modifying 

 his conception of the parallelism in the Bohemian fauna by removing 

 from his equivalent the lower portion of F, Novak (1886) showed 



