634 NEW YORK STATE MUSEUM 



between the deposits lying to the northwest and southeast of 

 the westernmost of the Appalachian series of overthrust faults 

 in New York and Canada. Indeed, he did recognize, so long ago 

 as 1866, that this overthrust marked in Canada the divisional 

 line between two basins, an eastern and a western.^ Though 

 we regard the correlations based on this view by Logan, as well 

 as the data from which the idea itself grew, as being at vari- 

 ance with the facts, his suggestion of distinct basins, it seems to 

 us, was far too important to deserve the oblivion to which it 

 has been assigned for all these years.^ 



Though abundant corroborative evidence of the existence of a 

 narrow barrier between the stratigraphically inharmonious 

 areas is afforded by the structural geology of the region in 

 question, it was perhaps scarcely to be expected that the geol- 

 ogists who attacked the problem chiefly or solely from that 

 side would find the true solution. It required detailed paleon- 

 tologic knowledge, particularly as to assemblages of fossils and 

 their geographic distribution, before the faunal distinctions 

 indicating separate provinces could be appreciated. Had the 

 geologists engaged on southern Appalachian problems received 

 a suggestion from the paleontologists of the striking dissimi- 

 larity marking the faunas pertaining to the lithologically 

 equally dissimilar Ordovicic rocks lying respectively on the 

 east and west sides of the Great Valley, it is scarcely conceiv- 

 able that they would have failed to grasp the leading facts in 

 the case. 



Excepting ^Yalcott, who, however, confined his fruitful com- 

 parative studies to the Cambric, it appears that no paleontol- 

 ogist having suflScient knowledge of the Ordovicic faunas of the 

 interior, and accustomed to fit his biologic results to strati- 

 graphy, paid much attention to these problems. 



*Geol. sur. Newfoundland. Rep't 1864; also reprint in 1881, p. 47. 



'This theory of Logan's was brought to the attention of the authors 

 but a few weeks ago. Occurring as it does as a note appended to Mur- 

 ray's report, it is not to be wondered that paleontologists remained in 

 Ignorance of its existence. 



