No. 4.] HUNT — ON CAMBRIAN AND SILURIAN. 439 



time, 219 species of organic remains, (comprising seventy-four 

 of Crustacea, and fifty one of graptolitidige) none of which, accord- 

 ins; to Mr. BilUmjrs, have been found either in the Potsdam or in 

 the Birdseye and Black River limestone. Twelve of the species 

 of the Levis formation are however met with in the Calciferous, 

 and five in the Chazy of the Ottawa basin, and the Levis is 

 therefore regarded by Mr. Billings as the connecting link between 

 these two formations. 



With regard to the British equivalents of these rocks, the 

 Levis limestone, according to Salter, corresponds to the Tremadoc 

 beds ; although the species of DlkeUocephalus found in the Levis 

 rocks are by him compared with those found in the Upper Lin- 

 gula flags or Dolgelly beds. The graptolitic strata of Levis 

 however clearly represent the Lower Llandeilo or Arenig rocks 

 of North Wales, the Skiddaw group of Sedgwick in Cumberland, 

 the graptolitic beds which in Esthonia, according to Schmidt, are 

 found below the orthoceratite-limestones, [Can. Naturalist, I. vi. 

 345] and those of Victoria in Australia, [Mem. Geol. Sur. Ill, 

 part 2, 255, 304.] In the Lower Llandeilo and Upper Trema- 

 doc beds there appears to be in North Wales, a mingling of 

 forms of the first and second faunas, as in the Levis and Chazy 

 formations. The latter was already, by Hall, in 1847, declared 

 to be beneath the Silurian horizon then recognized in Great 

 Britain. By its fauna it is comparatively isolated from the 

 strata both below and above it, and stratigraphically as well 

 as paleontologically it would appear to belong rather than to 

 the lower than to the higher rocks. According to a private 

 communication from Prof. James Hall, the Chazy limestone at 

 Middleville, Herkimer county. New York, to the south of the 

 Adirondacks, is wanting, and the basal beds of the Trenton 

 group (the Birdseye limestone) there rest unconformably upon 

 the Calciferous sandrock. 



The relations of the various members of the Quebec group to 

 each other, and of the group, as a whole, to the succeeding Tren- 

 ton and Hudson-River groups, require further elucidation. If, 

 as I am disposed to believe, the southeastward-dipping series of 

 the older strata near Quebec, exhibits the northwest side of an 

 overturned and eroded anticlinal, in which the normal order of 

 the strata is inverted, then the Lauzon and Sillery divisions, 

 which there appear to overlie the Levis limestones and shales, 

 are older rocks, occupying the position of the Potsdam or still 



