ANNIVERSARY ADDRESS OF THE PRESIDENT. 6 1 



present system of nomenclature exists nothing can disturb the 

 application of the title Cambrian to the rocks of the primordial series, 

 and of Silurian to the strata of the third fauna, or that series of 

 strata intervening between the Old Red Sandstone and the Lower 

 Llandovery. With the intermediate scries from the Llandovery to the 

 Lower Arenig " we have had incessant differences respecting nomen- 

 clature, proper limits of the groups, and sequence of fossils ; they 

 are still designated as Upper Bala, Caradoc, Middle Cambrian, and 

 Lower Silurian. This central system of the Lower Palaeozoic may 

 therefore well receive a name equally euphonious and significant of 

 the area where its strata are typically developed " *. 



jSTo division of the British sedimentary rocks has given rise to so 

 much controversy as the so-called Cambrian strata. At the present 

 moment they have no fixed or definitely-assigned horizon, either 

 base or summit, beginning or end ; their time-history, necessa- 

 rily their space-development also, rests upon no agreed or recog- 

 nized determination. Two, if not three, schools of research in these 

 lowest groups of rocks differ even among themselves as to the 

 uppermost limit that should be assigned to the term Cambrian, or 

 where in the field the line of demarcation should be drawn between 

 it and the Silurian, or at the base between it and the Pre-Cambrian 

 or metamorphic series. It is no part of my duty to enter into 

 details relative to the history of the controversy which has so long 

 occupied the minds and attention of the respective advocates of the 

 schools of Sedgwick and Murchison. 



The past ten years have witnessed great changes both in the 

 nomenclature and classification of the Cambrian rocks. The name 

 Cambrian, given by Sedgwick in 1838 to the whole group of strata 

 below the May-Hill Sandstone, has of late years again given rise 

 to much controversy. This critical research has been equally 

 important in its bearing upon the investigation of European and 

 American geology and the establishment of a corresponding no- 

 menclature for the succession and history of these oldest known 

 fossiliferous rocks on the globe. Whether we can rightly refer 

 the Dimetian, Arvonian, and Pebidian groups of Britain to the 

 Laurentian and Huronian of Canada is yet a question; that they 

 occur below the recognized Cambrian, there can be no doubt, both 

 from discordancy of strike, penological differences, and supposed 

 total absence of organic remains. Probably the great groups of rocks 

 comprised under the above names (Laurentian and Huronian), the 

 Archaean of Dana, may be the equivalents in time of our St.-David's 

 and North-Wales Pre-Cambrian ; and his Primordial or Cambrian 

 system (embracing the two series Acadian and Potsdam) may repre- 

 sent the lower portion of our fossiliferous Cambrian rocks, or those 

 so well defined and developed at St. David's, viz. the red shales and 

 flaggy beds with Lingulella ferruginea and L. jprimceva, the red, 

 purple, and grey grits, the Pluto ji/a-beds, the red, grey, and purple 

 flaggy sandstones, and the succeeding grey flaggy series, all five of 

 which are fossiliferous. Not only so, but these Pembrokeshire Cam- 

 * Loc. cit. p. 14. 



