WALCoiT.j SUMMARY — NORTHERN APPALACHIAN. 281 



It is quite probable that it is, from the character of the associated 

 fossils. As the vertical distribution of the fauua in the Olenellus zone 

 will be treated of in a future paper, further reference will not be made 

 *o it at preseut. 



The shales and slates superjacent to the Olenellus-bearing beds of 

 the Georgia slate, at Parker's quarry, do not apparently belong to the 

 Lower Cambrian, but are the representative of the middle portion of 

 the Cambrian section. This view was advanced by Prof. Jules Marcou, 

 in 1885, 1 except that he placed the same series of shales which occurs 

 at St. Albans beneath the Georgia slates or Olenellus zone. The stratig- 

 raphy was erroneous, but the suggestion that the St. Albans slates cor- 

 respond to the Paradoxides belt of the Atlantic Coast area will proba- 

 bly be found to be correct. In such an event Professor Marcou's name 

 St. Albans will be a useful addition to the nomenclature of the Cam- 

 brian group in northern Vermont. It will, however, be difficult to differ- 

 entiate between the St. Albans group and the superjacent beds carrying 

 the Upper Cambrian fauna. * 



In the group of sections taken across New Hampshire and Vermont 

 by Prof. C. H. Hitchcock 2 the Georgia series is called Potsdam and 

 Cambrian ; and in section xi, on PI. 17, the Georgia shales (Cambrian 

 of section) are represented as resting conformably on the magnesian 

 limestone (Potsdam of section) in the town of Milton. This is the same 

 as in the Georgia section a few miles to the north. The great mass of 

 argillites, east of the railroad track in the Georgia section, are placed 

 under the term Cambrian by Prof. Hitchcock, and the reference may 

 possibly be correct ; but as yet there have not been any recognized 

 Cambrian fossils obtained in it, either at this point or to the north or 

 south. 



In southern Vermont the Georgia slate series widens out, and includes 

 the great roofing-slate belt that extends through Rutland County and 

 into Washington County, New York. The outcrop of this series is nar- 

 row in the south part of Washington County, but it wideus rapidly in 

 Rensselaer County, occupying nearly the entire width of the county at 

 its southern boundary. At its greatest point of development in Wash- 

 ington County it consists of the following strata, as shown in a section 

 crossing the county in the towns of Greenwich and Salem, with its base 

 1£ miles west of North Greenwich post-office : 



Feet. 



(1) Massive layers ofimpure, shaly limestone embedded in irregular argillaceo- 



arenaceous shale, with numerous fossils of the Oleuellus fauna in the 

 limestone 340 



(2) Massive layers of line-grained, bluish gray, arenaceous limestone, that be- 



come almost a pure limestone in places 670 



About halfway of the mass LinguleUa ccelata, Hyolithellus micans, and 

 Lcperditia dermatoides occur. 



1 The Taconic System and its position in stratigraphic geology. Am. Acad. Proa, vol. 20, 1885, table 

 on p. 224. 



'Geological sections across Vermont and New Hampshire. Am. Mus. Nat. Hist., Bull., vol. 1, 1884, 

 pit. 16, 17. 



