Devonian Shales of Northern Ohio. 197 



referred for a discussion of the taxonomic features of this 

 nomenclature to the papers of Prof. C. S. Prosser' x " on the 

 nomenclature of the Ohio geological formations. Two of 

 these terranes, the Cleveland and Huron, are black shales, 

 while the third is a light colored more or less sandy shale. 

 Professor JMewberry,f in the original account of the formations, 

 here termed the Ohio shale group, recognized three distinct 

 terranes which he called, respectively, the Huron shale, the 

 Erie shale, and the Cleveland shale. At a later period, during 

 his earlier work, he confused the two black shale members of 

 the Ohio shale as exposed near Lake Erie and considered them 

 the same formation. Later, however, he discovered and 

 corrected:}: his mistake and correctly placed the "Erie," now 

 called Chagrin, shale between the two. Mr. Ulrich has fallen 

 into a similar error chiefly through theoretical deductions, as 

 already pointed out, in assuming that the Chagrin atid the 

 black shales represent distinct series of rocks. A somewhat 

 detailed account of the relations of these three shales of the 

 Ohio group to each other will, it is believed, be sufficient to 

 correct this latest misconception concerning them. 



A brief account of the essential characteristics of the three 

 formations of the Ohio shale group as they are developed in 

 their type sections, will be given before considering their char- 

 acteristics and relations elsewhere. The Cleveland shale, 

 which is the youngest member of the series, is represented in 

 the vicinity of Cleveland by a fissile black bituminous shale 

 which has a thickness ranging from about 35 feet in the east- 



PoUirhizodus, Cladodus, and Orodus, were found by him in the Cleveland 

 at Bedford. This is valid evidence that the fossils in question came from 

 what Professor Newberry considered the Cleveland. But concerning their 

 evidence for the Carboniferous age of the Cleveland it must be noted that 

 since Professor Newberry's time the range of one of these genera, Cladodus, 

 has been extended to the Middle Devonian (Eastman, Jour. Geology, vol. 

 viii, p. 35). Its occurrence in the Cleveland, therefore, is without special 

 significance as regards the age of the Cleveland. The two genera, Polyrhi- 

 zodus and Orodus, are in the Newberry collection of the American Museum 

 of Natural History. The Acting Curator, Dr. L. Hussakof. writes me that 

 there is some doubt as to whether the specimen referred to the former genus 

 really belongs to Polyrhizodus. The genus Orodus is represented by 21 

 recorded species from the lower part of the Carboniferous in the United 

 States. With this extensive representation in the early Carboniferous it 

 would be strange indeed if no Devonian forerunners had ever been found. 

 The representatives of this genus reported by Professor Newberry in the 

 Cleveland probably represent the Devonian heralds of the Carboniferous 

 host which followed. The principal stratigraphic points raised by Professor 

 Cushing have been fully discussed in the body of this paper. 



*The nomenclature of the Ohio geological formations : Jour. Geology, vol. 

 xi, pp. 533-537, 1903. 



Revised nomenclature of the Ohio geological formations : Geol. Survey 

 Ohio, Bull. No. 7, pp. 1-36, 1905. 



fGeol. Survev of Ohio, pt. 1, Rept. of Progress in 1869, 1870. pp. 18-21. 



JMon. U. S. Geol. Surv., xvi, p. 127, 1889. 



Am. Jour. Sci.— Fourth Series, Vol. XXXIV, No. 200.— August, 1912. 

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