52 THE CAMBRIAN. [bull. 81. 



sandstones on the Straits of Belle Isle, and on White Bay, Newfound- 

 land,*and by the slates of St. Albans and Georgia, Vermont. The Up- 

 per Potsdam is that of Wisconsin and Minnesota, represented in the 

 typical Potsdam of New York. This horizon is not recognized in the 

 northern part of Newfoundland, but occurs on Conception Bay, in the 

 southeastern part. The tabulation made by Logan has been followed 

 very largely by all writers upon American geology, and the succession 

 was not changed until 1888, when it was discovered that the St. John 

 group of Mr. G. F. Matthew was above the Lower Potsdam of Billings 

 and Logan. 



The Geological Survey of Newfoundland, under the direction of Dr. 

 Alexander Murray, added materially to our knowledge of the Lower 

 Paleozoic rocks. All the strata beneath the Calciferous or Quebec 

 group were referred to the Potsdam group. 1 In the neighborhood of 

 Canada Bay, on the east coast, the entire series referred to the Potsdam 

 has a thickness of 1,153 feet, of which the lower 700 feet belong to the 

 Lower Cambrian zone, as shown by Olenellus vermontana occurring in 

 the upper portion. 2 In the report of field work for 1868, Dr. Mur- 

 ray 3 describes the rocks about Conception Bay, in the southeastern 

 portion of the island. Of the lowest bed exposed on Manuel's Brook, a 

 small stream that flows into Conception Bay, he says : " On Manuel's 

 Brook a very coarse conglomerate may be seen, in strong and moder- 

 ately regular beds, resting directly upon the syenitic gneiss of the 

 valley above. * # # About 400 yards below the bridge the con- 

 glomerate is overlaid conformably by a set of dark brown or blackish 

 shales, * * * with some hard calcareous beds interstratified," and this 

 series extends down the stream nearly to the bay. 4 Dr. Murray also 

 describes, in a section at Topsail Head, a gray compact limestone in 

 strong solid beds, 1 to 2 feet thick, showing a vertical thickness of 

 about 100 feet, together with someinterstratified shale. The limestone 

 is subjacent to a darfi: brown, finely laminated shale. Detailed sections 

 are given of the shales and sandstones exposed on Kelly's and Great 

 Bell Islands, Conception Bay; the former has a thickness of 712 feet 

 and the latter of 476 feet. A summary of the rocks referred to the 

 Lower Silurian gives an entire thickness of 3,880 feet. 5 Figures of five 

 sections accompany the text, in which the unconformity between the 

 Lower Silurian rocks and the subjacent intermediate system or Huron- 

 ian and the Archean is well shown. The subjacent slates and Signal 

 Hill sandstones of Jukes are referred by Dr. Murray to the Cambrian 

 group on account of fossils having been found there, which Mr. Bill- 

 ings described as Aspidella terranovica and Arenicolites. 6 



1 Sequence and distribution of the rocks of the great Northern Peninsula. Geo]. Surv. New- 

 foundland, Rep. Prog, for 1864, Montreal, 1866, pp. 10, 44. Revised edition, 1881, pp. 5-47. 



2 Op. oii., p. 10. 



3 01 the sequence and distribution of the formations. Report upon the geological survey of New- 

 foundland for 1868, St. John's, 1868, p. 68. Revised edition, 1881, pp. 154-167. 



4 Op. cit.,p. 154. 

 »Op. cit., pp. 157-160. 

 • Op. cit., p. 144. 



