Marylaxd Geological Survey 29 



Marcellus with the sliales of Wissenbach in Xassau, as is proved by their 

 Goniatites, so analogous in form.' 



In recent years several geologists have considered the correhition of the 

 American Middle Devonian with European rocks of equivalent age, of 

 which the following are the most important. 



In 1889 Prof. H. S. Williams apparently correlated in a general way 

 the American Middle Devonian with " the Ilfracombe [England] beds of 

 Phillips, the Givetian limestone of Belgium, [and] the Stringocejjhalien 

 shales or limestones of the Eifel and Hartz regions." " In 1888 Prof. 

 Williams examined in the field typical sections of the Devonian rocks of 

 Devonshire, England, and later stated that " It appears probable that the 

 limestones of South Devonshire represent the general interval between the 

 close of our Corniferous [Onondaga] and the early part of our Chemung 

 formations." ' Professor Eenevier, in 189G, classed the Hamilton flags 

 and Marcellus shales together and regarded them as having been deposited 

 during the same general period of time as the Tentaculite slates (lower 

 part) of Thuringia, Hesse, Xassau, and Bohemia; the Wissenbach or 

 Orthoceras slates of Nassau; the Lenne slates (in part) of southern 

 Westphalia and the schists wdth Phacops potieri of Brittany; all of 

 which were correlated with the Couvinian age or stage, which he gave 

 as the lower one of the Middle Devonian or Eifelian epoch or series." 



Dr. Freeh draws the line between the Lower Devonian and the Middle 

 Devonian of New York at the top of the Upper Oriskany sandstone and 

 considers the Middle Devonian as composed of the Ulsterian and Erian 

 series, in the latter of which are the Marcellus shales, Hamilton beds 

 and Stringoceplialus beds of Canada.' At an earlier date Dr. Freeh 

 in his summary of the important occurrences of the Devonian gave the 



"■Ibid., p. 678; and Am. Jour. Sci., ibid., pp. .367, 368. 



^ Congres Geologique International. Compte Rendu, 4me. session, Loudres, 

 1888, 1891. Appendix A, p. 142. Also issued as: Report of the Sub-Committee 

 on the Upper Paleozoic (Devonic) by H. S. Williams, C, 1889, p. 22. 



^ Am. .Tour. Sci., 3d ser.. Vol. XXXIX, 1890, p. 36. 



■* Chronographe geologique. 2de edit, des Tableaux des Terrains sedimen- 

 taires. Compte-rendu du Congres Geologique International, Sixieme session, 

 AoGt, 1894, Zurich; Lausanne, Mars, 1897. 



''Lethaea geognostica, I Th. Leth83a palaeozoica. 2 Bd., 4 Lief., 1902, p. 690. 



