Maryland Geological Survey 73 



began the study of equivalent formations in Germany, along the lower 

 Ehinc Valley. In the end it was well that they were led to do this, for 

 " the Devonian system was founded upon one of the most unfavorable and 

 incomplete developments of that series of rocks and faunas known in any 

 part of the globe; a more precise scope was given to it by the work of its 

 founders, Murchison and Sedgwick, in the Ehineland, but even there no 

 determination of its lower limit was made. This admitted hiatus in the 

 typical succession "of Devonian to Silurian, is the parent of the prolific 

 discussions are ' post-Silurian ' and ' Hercynian ' faunas." ' 



In regard to the unraveling of the succession in Ehineland, the leading 

 student of the German Devonian, Professor Kayser,^ of Marburg Uni- 

 versity, states that Murchison and Sedgwick " first broke ground on the 

 continent in the Ehenish Schiefergebirge and their westerly extension, the 

 Ardennes, the largest and best developed Devonian area of western Europe, 

 which even up to the present day continues to add more to our knowledge 

 of the Devonian than any other [European] area. 



" The famous essay of the two English observers devoted to the Ehenish 

 mountains, appeared in 1842.' and its value was enhanced by the paleonto- 

 logical appendix contributed by d'Archiac and de Verneuil. In this 

 classical work, a part of the Taunus and Hunsriick was considered as 

 Cambrian; the chief mass of the Schiefergebirge as Silurian; a smaller 

 part, including the Eif el Limestone formation, as Devonian ; . . . . but 

 the classification of the older beds has needed considerable alteration. The 

 merit of undertaking this necessary revision is due to the ' Eheinischen 

 Uebergangsgebirges ' of Ferd. Eoemer, appearing in 1844, in which the 

 author shows that the chief mass of the Schiefergebirge must, according to 

 its fossils, be correlated not with the English Silurian, but with the 

 Devonian. 



" The extent of the Devonian in the Ehenish Schiefergebirge, the ac- 

 curacy of the observations made upon it, the completeness and variety of 

 the series, and its richness in fossils," make it the most important area 



' Clarke, Amer. Geol., voL xiv, 1894, p. 122. 



' Text-book of Comparative Geology. Translated by Philip Lake, London, 

 1893, pp. 89-91. 

 » Trans. Geol. Soc, 2d ser., vol. vi, p. 222. 



