0RI8KAKY FAUNA OF BECRAFT MOUNTAnf 83 



1 THE ARGUMENT FROM CORRELATION 



Since the proposition of Beyrich in 1867 to correlate the Helder- 

 bergian faunas of New York with strata in the Hartz mountains 

 which he believed to be of lowest Devonic age, the most careful 

 study of the lower Devonic has resulted in a like conclusion. Prob- 

 ably the detailed investigations following Beyrich's suggestion, by that 

 highly accomplished student of the Devonic, Prof. E. Kayser of Marburg, 

 effected the widespread acceptance of this correlation of the Helderbergian 

 with the lowest Devonic, specially among European students, with whom 

 little question of its propriety and exactitude has found expression 

 during the last decade. The history of the earlier stages of the dis- 

 cussion concerning the age of these and other beds which had been 

 at first regarded as of, upper Siluric age, was given by the writer 

 with some fulness 10 years ago,* and has again been presented 

 in a recent paper by Charles Schuchert. To these the reader 

 is referred. It is not germane to the purpose of this paper to bring 

 forward again the history of labors which have so far as evidence 

 from correlation goes, firmly established the Devonic age of this fauna. 

 To enumerate the names of those who have entered into this problem 

 is to give the full tale of the most experienced students of these 

 faunas, Kayser, Tschernyschew, Freeh, Barrois, Nov^k, Oehlert and 

 others. It is, however, quite unnecessary to seek in extra-limital 

 correlates the evidence of such Devonic age. 



2 THE ARGUMENT FROM THE INTRINSIC CHARACTER OF THE FAUNA 



With whatever emphasis extra-limital correlates bespeak the 

 Devonic age of this fauna, the strongest demonstration of its Devonic 

 affinities is intrinsic. In the work above cited the \vriter brought for- 

 ward in a tentative way a summation of uuch evidence, and since that 

 time has taken opportunity on several occasions to refer to the increas- 

 ing and convincing evidence of the proposition. No American geolo- 

 gist has since then given attention to the subject of the predominant 



* 8th ann. rep't N. Y. state geologist. 1889. p. C2-91. 



