Geolosaical Address at Manchester. 405 



o 



gan, James Hall, and others, by separating this rudimentary fauna 

 from that of the great Silurian series of life, of which stratigraphi- 

 cally it constitutes the conformable base. And if in Europe but few 

 genera be found which are common to this lower zone and the 

 Llandeilo formation (though the Agnostus and Orthis are com- 

 mon to it and all the Silurian* strata), we may not unreasonably 

 attribute the circumstance to the fact that the primordial zone of 

 no one country contains more than a very limited number of dis- 

 tinct forms. May we not, therefore, infer that in the sequel other 

 fossil links, similar to those which are now known to connect the 

 Lower and Upper Silurian series — which I myself at one time 

 supposed to be sharply separated by their organic remains — will 

 be brought to light, and will then zoologically connect the pri- 

 mordial zone with the overlying strata into which it graduates ? 

 Let us recollect that a few years only have elapsed since Mr. De 

 Verneuil was criticized for inserting, in his table of the Palaeo- 

 zoic fauna of North America, a number of species as being com- 

 mon to the Lower and Upper Silurian. But now the view of the 

 eminent French Academician has been completely sustained by 

 the discovery in the strata of Anticosti, as worked out by Mr. 

 Billings under the direction of Sir W. Logan, of a group of fos- 

 sils intermediate in character between those of the Hudson River 

 and Clinton formations, or in other words between the Lower and 

 Upper Silurian rocks. In like manner, a similar interlacing 

 seems already to have been found in North America, between the 

 Quebec group with its primordial fossils, and the Trenton de- 

 posits, which are, as is well known, of the Llandeilo age. 



"I have thus spoken out upon the fitness of adhering to the 

 classification decided upon by Sir Henry de la Beche and his 

 associates, long before I had any relation to the geological sur- 

 vey, which places the whole of the Lingula flags of Wales as 

 the natural base of the Silurian rocks. For English geologists 

 should remember that this arrangement is not merely the issue 

 of the view I have long maintained, but is also the matured 

 opinion of those geologists, in foreign countries and in our colo- 

 nies, who have not only zealously elaborated the necessary de- 

 tails, but who have also had the opportunities of making the 

 widest comparisons. 



" On the continent of Europe an interesting addition has been 

 made to our acquaintance with the fauna of one of the older beds 

 of the Lower Silurian rocks, or the Obolus green-sand of St. Pe- 



