368 CHARLES S. PROSSER 



^viz., the Portage, Ithaca, and Chemung — "appear to correspond 

 with the Devonian system of Mr. PhilHps."^ Tlie following year 

 Professor Hall gave the base as somewhat lower when he stated that 

 the Devonian system appears "to correspond to the Chemung and 

 Portage groups, and also to include a portion of the Hamilton."^ 

 In 1847 Professor Hall stated that 



With the Schoharie grit, commences a series of strata containing fossils as distinct 

 from those of the preceding formations, as these are from the lower division. We 

 here, for the first time, recognize several species that are regarded as Devonian 

 forms; and if zoological characters are to be paramount, we are compelled to 

 unite all the succeeding strata as of Devonian age.^ 



Finally in 1859, he raised the question whether even the Oriskany 

 sandstone might not be considered as of Devonian age. For he wrote 

 as follows concerning 



the line'of demarkation for the Silurian and Devonian systems. Shall the advent 

 of the Oriskany sandstone, with its Spirijer of dichotomizing costa?,be the division ? 

 Or shall we look for some more marked and more readily defined and recognized 

 feature for the distinction between what are regarded as two great geological 

 systems ?•* 



So far as the writer is aware, de Verneuil in 1847 was the first 

 geologist definitely to correlate the younger formations of the New 

 York system with subdivisions of the Devonian system of Europe. 

 He made the base of the Oriskany sandstone the dividing line between 

 the Devonian and Silurian systems;^ correlated the Hamilton, Tully, 

 Genesee, Portage, and Chemung with the formations of the Eifel 

 and Devonshire, and the Marcellus with the shales of Wissenbach 

 in Nassau, as is proved by their Goniatites, so analogous in form.^ 



In recent years several geologists have considered the correlation 

 of the American Mesodevonian with European rocks of equivalent 

 age, of which the following are the most important: 



1 Geology of Neiv York, Part III, p. 171. 



2 Ibid., Part IV, p. 20. 



3 PalcBontology of New York, Vol. I, p. xvii. 

 A Ibid., Vol. Ill, Part I, p. 42. 



5 Bulletin de la Societe Geologique de France, Second Series, Vol. IV, p. 677; also 

 American Journal of Science, Second Series, Vol. V (1848), p. 367, on the parallelism 

 of the Palffiozoic deposits of North America with those of Europe, translated by James 

 Hall. 



(>Loc. cit., p. 678; and American Journal of Science, loc. cit., pp. 367, 368. 



