walcott.J POTSDAM SANDSTONE 113 



as great as tbat of the ISSp paper. The S wanton slates, of Hudson 

 age, and the Phillipsburgh and Point Levis formation of Calciferous 

 age, are placed with the Potsdam sandstone; while in the Lower Ta- 

 conic we fiud the sandstones of Great Bell Island, which are the geo- 

 logic equivalent of the Potsdam sandstone. 



During the summer of 1888 Mr. 0. D.Walcott visited Newfoundland 

 and studied 1 a section on Manuel's Brook, Conception Bay, that extends 

 from the Archean gneiss up to the Olenellus and Paradoxides zones. 

 In this unbroken section it was found that the Olenellus fauna occurred 

 at the base and the Paradoxides fauna above. This necessitated a 

 revision of the classification of the Cambrian. The Lower Cambrian 

 with the Olenellus fauna is at the base; next the Middle Cambrian 

 with the Paradoxides fauna, and lastly the Upper Cambrian or Potsdam 

 zone, at the summit of which the Dikellocephalus fauna occurs. This 

 correlation places the u Red Saudrock " series, the Georgia shale and 

 slate series, the ll Granular Quartz," and the. " Upper Taconic " of Em- 

 mons beneath the Middle Cambrian or Paradoxides zone of the Atlantic 

 coast. 



In a paper on the fauna of the Olenellus zone 2 a brief historical re- 

 view is given of the rocks referred to the Olenellus zone in Vermont 

 and eastern Xew York, and also an account of the sections and the dis- 

 tribution of the fauna. 



In a paper read before the Geological Society of America, December 

 30, 1300, Dr. J. E. Wolff noted the discovery of fossils of supposed 

 Lower Cambrian age in the limestones of the East Rutland Valley, Ver- 

 mont. The limestones rest conformably upon the basal qnartzite car- 

 rying the Olenellus fauna. 3 



Potsdam sandstone. — The Potsdam sandstone of the Adirondack area 

 appears only in a few small outcrops in Vermont and eastern New York. 

 According to Prof. C. IT. Hitchcock, there are three different localities 

 in Vermout: 4 near the Lake Champlain shore in West Haven, Orwell, 

 and the east part of Shoreham, in the counties of Addison and Rutland. 

 There were none of these of sufficient importance to be indicated on the 

 map of 1877. The outcrops in eastern New York are practically a con- 

 tinuation of the Vermont exposures. They occur in the vicinity of 

 Whitehal 1 , New York, and south to Fort Ann, Washington County. 



In the review of the references made to the u Red Saudrock n series 

 of Vermont, frequent mention has been made of its correlation with the 

 Potsdam sandstone as well as of the correlation of the "Granular 

 Quartz" with the Potsdam sandstone of the Adirondack area. As now 

 known, these two belong to distinct geological horizons, as claimed by 



stratigrapbical succession of the Cambrian faunas of North America. Nature, rol. 38, 1868, p. 

 551. 



* Walcott, C D. The fanna of the Lower Cambrian or Olenellus zone. 10th Ann. Rep. D. S. Geolog- 



■irvey, 1890, pp 

 •Boll. Geo). Soc. Aim i 1891, pp. 331-337. 



•Hypo/oic aud Pah ozoic - ks. Report on the geology of Vermont, vol 1, 1861, p. 265. 



Bull. 81 8 



