280 On the Structure and Position of Eozoon Canadense. 



is known by the designation " Lingula-flags." For the whole 

 series of stratified rocks underlying the original Silurian 

 system of Sir B,. Murchison, the names of Cambrian or 

 Cumbrian, indicative of its special development in North 

 Wales and Cumberland, were proposed by Professor Sedg- 

 wick ; but geologists for some time hesitated in admitting it 

 as a distinctly characterized group. The fossil types which 

 it contained did not seem to differ so much from those of the 

 Lower Silurian strata, as to justify the separation of the Cam- 

 brian from the Silurian fauna; and it was argued by Sir 

 Eoderick Murchison that there was more reason for carrying 

 downwards the base of his Silurian system, so as to make it- 

 include the Lingula flags and the slates which intervene 

 between it and the Llandeilo flags, than for admitting the 

 existence of any pre- Silurian life. Even as late as 1851 we 

 find so impartial and highly- qualified a judge as Sir Charles 

 Lyell thus expressing himself on this point {Manual of Ele- 

 mentary Geology, 3rd ed., p. 361) : — (( Below the Silurian 

 strata in North Wales, and in the region of the Cumberland 

 Lakes, there are some slaty rocks devoid of organic remains, 

 or in which a few obscure traces only of fossils have been 

 detected, for which the names of Cambrian and Cumbrian 

 have been proposed. Whether these will ever be entitled, by 

 the specific distinctness of their fossils, to rank as independent 

 groups, we have not yet sufficient data to determine." 



The required data had been already furnished, however, by 

 the labours of M. Barrande in Bohemia; in which country 

 the older stratified rocks are developed even more remarkably 

 than in Britain. Although scarcely more than twenty species 

 of fossils had been previously obtained from this locality, M. 

 Barrande had already acquired in 1850 no fewer than 1100 

 species; namely, 250 crustaceans (chiefly trilobites), 250 cepha- 

 lopods, 160 gasteropods and pteropods, 130 acephalous mol- 

 lusks, 210 brachiopods, and 110 corals and other fossils. This 

 vast assemblage he found to comprise not merely the equiva- 

 lents of the Upper and Lower. Silurian fauna, but also a fauna 

 clearly distinguishable from the latter, and designated by him 

 " primordial," under the belief that it afforded evidence of the 

 first appearance of life on this planet, and that consequently 

 no fossiliferous strata of older date would or could ever be 

 discovered ; — an anticipation as vain as that which the founder 

 of the Silurian system had entertained respecting the strata 

 which he originally adopted as its base. 



The peculiarity of the so-called " primordial fauna" specially 

 consisted in the distinctness of its Trilobites from those of the 

 Lower Silurian strata ; not only the species, but even many of 

 the genera, discovered by M. Barrande having been previously 



