1857.] MURCHISON SILURIAN ROCKS OF SCANDINAVIA. 49 



which lie at a considerable distance from the junction with the Silu- 

 rian rocks, the strata are charged with many well-known Devonian 

 fossils. 



Conclusion. 



In the opening pages of this Memoir a running comparison was 

 instituted between the different subformations which constitute the 

 Silurian basin of Christiania in Norway and their British equivalents ; 

 and, considering the distance of the Norwegian tract from our own 

 country, the coincidence in the succession of fossils is truly re- 

 markable. 



The point, however, of the labours of M. Kjerulf to which I now 

 particularly recall attention, is that in the very lowest fossiliferous 

 zone (the alum-slates of Norway) the types of Trilobites which were 

 supposed by some authors to be confined to that zone are united 

 with the Orthis calligramma and the Didymograpsus geminus, spe- 

 cies known as occurring in unquestionable Lower Silurian British 

 rocks. Any one of the published sections across the western parts 

 of Shropshire, i. e. from the Longmynd over the Stiper Stones, shows 

 what the parallel order is in Britain*. 



Having for the last twenty-four years considered and described 

 the Stiper Stones as the true physical base of the Silurian series of 

 strata, it has been satisfactory to me to detect recently, in the black 

 schists associated with the siliceous flagstones of that ridge, additional 

 fossils which so intimately connect them with the Llandeilo formation, 

 that the additional evidence in the new edition of ' Siluria ' will, I 

 believe, be conclusive as to the natural base of the British Silurian 

 rocks. For neither in Shropshire nor in Norway can we draw a 

 line of physical or zoological demarcation between these basement- 

 strata, whether termed Lingula Flags, Stiper Stones, or iVlum Slates, 

 and those overlying schists into which they graduate, and of which 

 they form an integral part. 



This union is indeed particularly well marked in Scandinavia, 

 where the alum- slates are simply a mass of black schist, which is no 

 more capable of separation from the overlying beds of similar cha- 

 racters than one bed of the Lower Lias or any other secondary shaly 

 subformation is from another. 



Seeing the dissimilarity of forms which prevails throughout the 

 Silurian series of Bohemia, as described by M. Barrande, when we 

 look to the distinction between the fossils of each of the subdivi- 

 sions, and especially when we compare such subdivisions with their 

 acknowledged equivalents in the northern Silurian zone now under 

 consideration, it seems to me to be impossible to establish a new 

 classification of the Lower Palaeozoic rocks by eliminating the " Zone 

 Primordiale " of that distinguished author from the natural-history 

 system in which he has himself placed it. In Bohemia the " Zone 

 Primordiale " is as integral a part of the Silurian basin so called, as 

 the Stiper Stones were in my original classification. If I am not 



* See the ' Silurian System,' pi. 32. fig. 1, &c., and ' Siluria,' diagram, p. 29. 

 VOL. XIV. PART I. E 



