Notes upon the Geology of the Western States. 57 



are a few which appear to be identical with those of the carbon- 

 iferous hmestone of Europe, and one of these I am not able to 

 distinguish from Producta hemispherica.* 



I have here already pointed out the relative position of three 

 successive formations ; first, the old red sandstone group, corres- 

 ponding both in its upper and lower part with the same series in 

 Europe ; secondly, a limestone, which is clearly the equivalent of 

 the carboniferous limestone ; and thirdly, a conglomerate which 

 is the fundamental rock of the coal formation, and may therefore 

 represent the millstone grit of Great Britain. It thus becomes 

 quite unnecessary in this place to point out the striking similarity 

 in position and other characters of the great coal formation, with 

 that of Great Britain and other parts of Europe. 



Continuing the groups of New York as the standard of refer- 

 ence, we next arrive, in the descending order, to the great group 

 of fossiliferous shales so well developed along Cayuga and Sen- 

 eca lakes, and known as Marcellus, Skaneateles, Ludlowville, 

 and Moscow shales, which, for the sake of brevity, I shall speak 

 of under the name of the Ludloioville group. This great group, 

 which occupies in New York a thickness not less than one thou- 

 sand feet, and contains a greater number of individual fossils than 

 nearly all the other groups, thins out in its western prolongation, 

 losing at the same time its distinctive paleontological character, 

 so that when we ajnje at the falls of the Ohio, (Louisville, Ky., 

 and New Albany, 1^,) it is represented by one hundred and four 

 feet of black shale,t nearly or quite destitute of fossils. Farther 

 west this shale descends beneath the higher groups, and I was 

 not able to discover it on the Mississippi. 



The " Helderberg limestone group" follows in the order of suc- 

 cession : next below is the " Onondaga salt group," and below 

 this, the Niagara lim,estone and shale group. In New York, 

 these form three very distinct and important masses, extending 

 over great areas and with very considerable thickness. The first 

 is in greatest force in the Helderberg mountains, in Albany 

 county, and in Schoharie, where the whole thickness is four 

 hundred or five hundred feet. This group gradually thins west- 



* I have since been able to identify several other species of fossils from this rock 

 with those of the carboniferous limestone of England. 



t I am indebted to Dr. Clapp of New Albany, who has bored through this shale, 

 for this accurate information of its thickness. 



Vol. XLii, No. 1.— Oct.-Dec. 1841. 8 



