TRANSACTIONS OF THE 8KCTI0NS, 98L 



I take this opportunity, however, of reiterating the opinion I have expressed in 

 my work ' Siluiia,' that to whatever extent the primordial zone of Barrande be 

 distinguished by peculiar fossils in any given tract from the prevalent Lower Silu- 

 rian types, there exists no valid groimd. for difiering from BaiTande, De Vemeuil, 

 Logan, James Hall, and others, by separating this rudimentary fauna from that of 

 the gi-eat Silmian series of life of which stratigi'aphically it constitutes the conform- 

 able base. i\iid if in Europe but few genera be yet found which are common 

 to this lower zone and the Llandeilo foiiuation (though the Aynostus and Orthis 

 are common to it and aU the Silurian sti-ata), we msty not imreasonably attribute 

 the circmiistance to the fact that the primordial zone of no one coxmtry contains 

 more than a veiy limited number of distinct forms. May we not, therefore, infer 

 that in the sequel other fossil links, similar to those which are now known to con- 

 nect the Lower and Upper Silmian series — ^which I myself at one time supposed to 

 be shari^ly separated by their organic remains — wiU be brought to light, and will 

 then zoologically connect the primordial zone with the overlying strata into which 

 it gi-aduates ? Let us recoUect that a few years only have elapsed since M. de 

 Vemeuil was criticised for inserting, in his Table of the Palaeozoic Fauna of North 

 America, a number of species as being common to the Lower and Upper Silurian. 

 But now the view of the eminent French Academician has been completely sus- 

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

 under the direction of Six W. Logan, of a group of fossils intermediate in character 

 between those of the Hudson River and Clinton formations, or, in other words, be- 

 tween 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 deposits, which are, as is well known, of the 

 Llandeilo age. 



I have tlius spoken out upon the fitness of adhering to the classifications decided 

 upon by Sir Henry De la Beche and his associates long before I had any relation to 

 the Geological Survey, and which places the whole of the Lingula-flags of Wales 

 as the natural base of the Silm-ian 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 coimtries and in our 

 colonies who have not only zealously elaborated the necessaiy details, but who 

 have also had the opportunities of making the widest comparisons. 



On the continent of Europe an interesting addition has been made to oui" ac- 

 quaintance with the fauna of one of the older beds of the Lower Silurian rocks, 

 or the Obolus greensand of St. Petersburg*, by our eminent associate, Ehrenberg, 

 He has described and liguredf four genera and ten species of microscopic Ptero- 

 podfl, one of which he names Panderella Silurica ; the generic name being in honour 

 of the distinguished Kussian palaeontologist. Pander, who collected them. It is 

 well to remark, that as the very grains of this Lower Silurian greensand seem to 

 be in great part made up of these minute organisms, so we recognize, in one of the 

 oldest strata in which animal life has been detected^ organisms of the same nature, 

 and not less abimdant than those which constitute the deep sea-bottoms of the 

 existing Mediterranean and other seas. 



Before I quit the consideration of the older palseozoic rocks, I must remind you 

 that it is through the discoA^ery, by Mr. C. Peach, of certain fossils of Lower Silu- 

 rian age in the limestones of Sutherland, combined with the order of the strata, 

 observed in the year 1827 by Professor Sedgwick and myself, that the ti-ue age of 

 the largest and overlying masses of the crystalline rocks of the Highlands has been 

 fixed. The fossils of the Sutherland limestone are not indeed stiictly those of the 

 Lower Silurian of England and Wales, but are analogous to those of the calcife- 

 rous sand-rock of North America. The 3Iaclurea is indeed known in the Silurian 

 lunestone of the south of Scotland ; but the OjjMleta and other forms are not found 

 until we reach the horizon of North America. Now, these fossils refer the zone of 

 the Highland limestone and associated quartz-rocks to that portion of the Lower 

 Silmian which fonns the natural base of the Trenton series of North America, or 

 the lower part of the Llandeilo foimation of Britain, The intermediate formation 



* See ' Eussia and the Ural Mountains.' 



t Monats-Berjcht d. Kiinig. Akad. der Wiss. Berlin, 18 April, 1861. 



7* 



