and the Taconic System. , 381 



Thompsoni and 0. Vermontana, with what appears to be an 

 Arionellus, besides Oholus, Capulus, and a large spirally marked 

 coral resembling Zaphrcntis. These rocks, whi(^L evidently rep- 

 resent the Primordial Zone, arc overlaid by others containing the 

 chara'-teristic fossils of the Calciferous sandroc-k and the compound 

 graptulites of the Quebec gi'(Mip. Tliese primordial trilobites 

 then overlie the sandstone with SroUthus, but as we Lave 

 elsewhere observed, thai species appears unlike the ScolitkuS 

 from the Potsdam of Lake Champlain, and should not be 

 too much relied upon for fixing the geological age of this forma- 

 tion. It is not improbable that the true equivalent of the Cono- 

 cephalites and Lingula sandstones of Lake Champlain will be 

 found in some of the strata above tlie Olenus beds of Belhsle. 



We have seen that Emmons, guided by a false notion of the age 

 of the Green Mountain gneiss which led him to admit an inversion 

 of the whole series, placed the shales which form a portion of the 

 Primordial Zoae high in the second fauna, above the whole Que- 

 bec group. On entirely difiierent ground. Hall assigned the shale 

 containing OZe/2W5— two species of which genus he described in 184Y 

 in the 1st Vol. of the Palaeontology of New York, — to the Hudson 

 group. In this, as Barrande shows, Mr. Hall felt himself justified 

 by the authority of Hisinger, who in his great work on the fossils 

 of Sweden, Lethcea Suecic//, 1887, gives the succession of palaeo- 

 zoic rocks in Sweden as follows in ascending order; 1. Fucoidal 

 sandstone; 2. Orthoceratite limestone; 3. Alum slates with 

 Olenus ; 4. Argillaceous slates with graptolites, etc. 



The O^mws slates, said by Hisinger to overlie the orthoceratite 

 limestone, (corresponding to the Trenton,) Mr. Hall unhesitatingly 

 regarded as the equivalents of the Hudson group, in which Olenus 

 was to be looked fo)' as a characteristic fossil, and hence the strata 

 containing these trilobites were, on the authority of Hisinger, 

 regarded as belonging to the summit of the second fauna. In 

 reaht}^ however this order assigned by Hisinger to the formations 

 of Sweden is false, since the alum slate with Olenus lies below, 

 and the graptolitic slate above the orthoceratite limestone. This 

 error of Hisinger is the more strange since he had long before, as 

 Barrande shows, indicated the true succession of these rocks, and 

 is perhaps a mistake of the copyist or printer ; it is the more to 

 be regretted as his authority had caused it to be adopted by Mr. 

 Hall in America. [Geol. of Lake Superior^ Foster and Whitney^ 

 II. pp. 298 — 318.) The alum slate with the underlying sand- 

 stone represents in Sweden the primordial zone. 



