50 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 6, 



justified in referring to my sections and memoirs of the years 1833, 

 1834, when I classed the Stiper Stones with the overlying deposits, 

 I am at all events entitled to adhere to that view, now that M. Bar- 

 rande also unites his " Zone Primordiale" with the overlying strata ; 

 and since, fully aware of the distinction between its fossils and those 

 which succeeded it in Bohemia, this eminent geologist continues to 

 classify it with the Silurian System. 



We ail know how in those secondary and tertiary rocks which have 

 been most examined there is often a marked discrepancy in the fossils 

 of each succeeding stratum, so long as we examine a limited area only, 

 and how such sharp separation and isolation of the former inhabitants 

 of the seas vanishes when the same strata are followed over great 

 distances. So is it when, quitting our insular area and extending 

 our researches to Norway, we find strata of black schist, mineralogi- 

 cally resembling the Lingula-flags or the schists of the Stiper 

 Stones, and occupying the same place in the geological series, to be 

 charged with some of the organic remains which in Britain are 

 peculiar to that band, mixed up with species which are known in our 

 own Llandeilo rocks. Again we observe that, as in the Stiper Stones 

 of Shropshire, there is in Norway a vast underlying series of slates 

 and quartzose rocks like those of the Longmynd ; so also are the beds 

 into which the alum- schists pass upwards laden with many species 

 of fossils which are with us in the Lower Silurian rocks of Llan- 

 deilo age. 



The attempt to separate the alum-schists of Scandinavia from the 

 overlying beds with which they are united in numerous natural 

 escarpments is indeed forbidden on stratigraphical, lithological, and 

 zoological grounds ; and as Linnaeus and every subsequent explorer 

 of Scandinavia have connected them, so I confide in the belief that 

 they constitute, by their organic remains, the best base we have been 

 able to trace of that which I call Silurian life. 



In comparing the Silurian rocks of Scandinavia and Russia with 

 those of Britain, there is no feature by which the whole system is 

 seen to be better. characterized in those countries than by containing in 

 its central part a formation distinguished from the rocks above and 

 below it by certain species of Pentameri, of which the Pentamerus 

 oblongus and the P. lens are the prevailing types. 



Having satisfied myself, in my own country, that the lower portion 

 of this formation is (as I always maintained) related by its organic 

 remains to the Caradoc formation, and that the upper part of it is 

 charged with a number of shells of the Wenlock age (though still 

 intermixed with the peculiar Pentameri and a few Lower Silurian 

 fossils), I have deemed it right to assign to the deposit a separate 

 and intermediate place in the table of Silurian strata. 



I have named this formation " Llandovery rocks," reverting to that 

 tract of South Wales which was originally described in detail, and 

 where both the lower and upper members of the group, and their re- 

 lations to the underlying and superjacent rocks, are clearly exhibited. 



It is the upper member only of these Pentamerus-rocks which is 

 exhibited at May Hill, on the west flank of the Malverns, and also in 



