whxiamb.] ITALL's PARALLELISM OF THE PALEOZOIC. 73 



stone are said to indicate a "close affinity with the Carboniferous;" the 

 Cephalopoda of the Marcellns and the Brachiopoda and some Cephal- 

 opoda of the Chemung and Hamilton groups are reported as " of Carbon- 

 iferous facies." Again, the Brachiopods and Lamellibranchs of tlie 

 Chemung and Ilamilton, and the Brachiopods of the Corniferous are in- 

 dicated as presenting a " Devonian facies," while the Lamellibranchiata 

 and Orthocerata of the Chemung and Hamilton, the Cephalopoda of the 

 Corniferous, and the Cephalopoda and Crustacea of the Schoharie grit 

 are regarded as " equivalents of the corresponding faunas of the Lud- 

 low rocks in Europe." 



This indicates considerable confusion, and the inference to be drawn 

 from a study of these results is that the determination of the fossils 

 was not sufficiently accurate to make the comparisons with precision. 

 •It is probable that the difference between the species which were de- 

 fined as "Carboniferous," or "Devonian," or "Upper Silurian (Lud- 

 low) " in Europe, belonging to the same genera, was not so great as the 

 difference which the species, belonging to the same horizon, might 

 exhibit on the two sides of the ocean ; but at this stage in the progress 

 of paleontology there was apparen tly very little appreciation of the 

 amount of variation which species of the same genus undergo during 

 the same geologic epoch. 



Hall was of the opinion that the Upper Helderberg of the New York 

 system represented the Ludlow group of Murchison, and while he rec- 

 ognized the fact that the Ludlow beds were separated by the English 

 from the Devonian, he insisted that the fossils of the Ludlow were 

 represented by the fossils of the Schoharie grit and Corniferous lime- 

 stone more closely than by any of our Lower Helderberg species. He 

 insisted that either the Ludlow beds belonged to the Devonian or that 

 there must be some considerable gap in the New York series between 

 the Lower Helderberg and the Upper Helderberg. He said, after 

 stating that he could not agree with M. de Verneuil in placing the 

 Lower Helderberg limestones in parallelism with the Ludlow: 



Leaving out of consideration the Oriskany sandstone and Canda-Galli grit, we feel 

 disposed to regard the Schoharie grit as possessing zoological features more in accord- 

 ance with those of the Lower Ludlow series than any other rock in our classification. 

 We shall thus place it for the present. 1 



And in his table of equivalents the Wenlock series is represented by 

 the Clinton group in part, Niagara group, and Lower Helderberg lime- 

 stones ; and the Ludlow series and Devonian system are represented 

 by our Upper Helderberg limestones, Hamilton group, Chemung group, 

 and the Red sandstone and shale of the Catskill Mountains. 2 



As indicative of the stage of refinement reached in the identification 

 of species and its results, the following quotations may be made : 



Although it is not difficult to find the evidence of a general parallelism in our suc- 



1 Foster and Whitney, Kept, on Lake Superior, pt. 2, p. 310. * Ibid., p. 317. 



