The Cuboides Zone. 



For several years I have been seeking some point in the upper Paleozoic 

 series of Europe and America at which precise correlation might be possible. 



It is difficult to find an American Devonian species which does not differ 

 as much from its closest European representatives as it does from its nearest 

 allies in the formations below or in the formations above its normal horizon. 

 Therefore, correlation by mere numerical comparison of lists of fossils must 

 be regarded as having a normal error of at least the length of an ordinary 

 geologic age, or etage, as those terms are used by the International Congress 

 of Geologists. 



The sharpness of definition of the fauna of our New r York Tully limestone 

 at the base of the upper Devonian, when it is not confused with the Hamil- 

 ton fauna below (as it has frequently been), led me to select it for special 

 study. It is directly comparable with the " Cuboides Schichten " of Emanuel 

 Kayser, who has done more than any one else to classify the formations and 

 faunas of the Devonian rocks of Germany. 



The name "Cuboides Schichten" was applied by Kayser to the calcareous 

 shales and argillaceous and nodular limestones of Aachen (Aix la Chapelle) 

 and of the Rhenish provinces of Prussia, which immediately follow the 

 Stringocephalus limestone.* Across the border in Belgium they are called 

 by Gosselet f the Frasnien limestone and shales ; in the Harz it is the Iberger 

 limestone. 



For this northern part of Europe the Devonian history of sedimentation 

 was, first, coarser deposits, sands, and, in some cases, conglomerates, with 

 frequent evidence of volcanic disturbance marking the lower Devonian and 

 beginning of the middle Devonian periods, followed b} r limestones, thick and 

 massive, in the Eifel ; in other regions often associated with calcareous shale 

 and argillaceous shale, and in the upper part purer limestone, as at Pelm 

 reaching great thickness — over a thousand feet — and characterized by the 

 presence of String ocephalus burtini. 



This String ocephalus limestone is recognized in the Eifel district, in the 

 northwest Harz, in Nassau and Westphalia, and in southern Belgium and 

 northern France. It is the Givetien limestone of Gosselet and Dewalque. 



Above the String ocephalus limestones follow impure limestones or calcare- 

 ous shales (the German Mergel), called by C. F. Roemer £ Verneuili Schiefer, 

 and by F. A. Roemer,§ in the northwest Harz, Iberger Kalk and Goslarer 

 Schiefer — the Frasnien of Gosselet aud the Belgian and French authors. 



* Emanuel Kayser: Das Devon der Gegend von Aachen, Zeitschr. d. Deutschen geologoschen 

 Gesetlschaft, Jahrg., 1870, p. 848. 

 t M. J. Gosselet : Esqnisse Geologique du Nord de la France, 1880, fasc. I, p. 95. 

 JC. F. Roemer: Das Rheinische (Jebergangsgebirge, 1844. 

 f F. A. Roemer: Beitriige zur geologischen Kenntniss des Nordwestlichen Harzgebirges, 1850. 



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