Oh. XXVIL] 



CAMBRIAN GROUP. 



575 



I have little doubt, have been universally accepted, since lie bad 

 acquired full right to give a name to the new group or system of 

 rocks, the position and characteristic fossils of which he had first 

 truly denned. 



The term "primordial" was intended to express M. Barrande's own 

 belief that the fossils of Etage C afforded evidence of the first ap- 

 pearance of vital phenomena on this planet, and that consequently 

 no fossiliferous strata of older date would or could ever be dis- 

 covered. 



I have been opposed from the first to a nomenclature the adoption 

 of which would seem to imply the acceptance of such a theory, for I 

 always felt sure, on contemplating the past history of geology, that 

 we had not yet pushed our inquiries into the past so far as to lead us 

 to despair of extending our discoveries at some future day, when vast 

 portions of the globe hitherto unexplored should have been thorough! j t 

 surveyed. * 



The term "Cambrian" had, long before 1846, been applied by Prof. 

 Seclgwick to rocks, some of which we now know to be of contem- 

 poraneous date with Barrande's "primordial zone."' Sedgwick had 

 begun his exploration of these rocks in 1831, and in 1843 published 

 memoirs on what he then termed the protozoic rocks of North Wales, 

 giving detailed sections by which the geological structure of an intri- 

 cate region was admirably worked out. 



Large portions of the strata both of South and Xorth Wales at first 

 called Cambrian, and supposed to be older than the Silurian rocks of 

 Murchison, were afterwards proved by our surveyors, chiefly by the 

 labors of Prof. Ptamsay, to be the equivalents of the Lower Silurian 

 rocks above described. 



The following table will show the succession of the strata in England 

 and Wales which belong to the Cambrian group or the fossiliferous 

 rocks older than the Lower Llandeilo, to which are added the Lau- 

 rentian formations of Canada, as the oldest in the world in which 

 organic remains have yet been found : 



CAMBRIAN" GROUP. 



Upper 

 Cambrian 

 Rocks. — 

 ("Primor- 

 dial Zone" 

 of Bar- 

 rande). 



Prevailing Litho- 

 logical Characters. 



Thickness 

 in Feet. 



rr, -, ( Dark earthy slates 



i. Tremadoc ) . Al _ J . „■,... 



slates. 



\ 



with 

 ore. 



pisolitic y 2000 



Lingula 

 flass. 



{Micaceous flag- ) 

 stones and >• 



shales. ) 



Organic Eemains. 



T Trilobites of genera 



partly Silurian and 



J partly Primordial 



of Barrande. Bel- 



lerophon ; Ortho- 



(_ ceratite ; Theca. 



about ■{ 

 6000 



Trilobites ; Olenus, 

 Conocoryphe ; Pa- 

 radoxides ; Phyl- 

 lopod crustacean • 

 Brachiopoda; Cys- 

 tideans. 



