574 CAMBEIAN GROUP. [Ch. XXYII. 



Sir Roderick Murchison after five years' labor, in 1839, when his 

 " Silurian System " was published, that these formations could from 

 that period be recognized and identified in all other parts of Europe 

 and in North America, even in countries where the fossils differed 

 specifically from those of the classical region in Britain, where they 

 were first studied. But it was not till the year 1846 that M. Joachim 

 Barrande, after ten years' exploration of Bohemia, and after collecting 

 more than a thousand species of fossils, ascertained the existence in 

 that country not only of the equivalents of the two formations above 

 alluded to, but of another set of strata, characterized by a new and 

 distinct fauna, to which, in the introduction to a treatise on trilobites, 

 he gave the name of Etage C, or the " first fauna." His two first 

 stages, A and B, consisted of crystalline and metamorphic rocks, and 

 unfossiliferous schists. In the zone C, called soon afterwards by him 

 "primordial," he had discovered in 1846 no less than twenty-six spe- 

 cies of trilobites contained in shales and slates of considerable thick 

 ness, all of them belonging to new species and the greater part of 

 them to new genera, called by him Paradoxides, Conocephalus (syn. 

 Conocoryphe), Ellipsocephalus, Avion, Sao, and Hydrocephalus, and 

 some of them to the genus Agnostics, the only form common to his 

 first and second fauna, the latter corresponding to the Lower Silurian 

 of Murchison. M. Barrande classed this first fauna as the oldest 

 member of the Silurian period, applying the term Silurian in Sir R. 

 Murchison's sense as comprehending all the fossiliferous strata older 

 than the Devonian. He spoke of it as occupying " le meme horizon 

 que les formations fossiliferes les plus anciennes de Suede, de Norvege 

 et des Isles Britanniques ; " and he added, still speaking of Etage C, 

 " II forme done la base des terrains protozoi'ques, selon la derniere 

 classification du Rev. Professeur Sedgwick." * It was impossible in 

 1846 for M. Barrande to make a nearer approach towards a just cor- 

 relation of the Bohemian and British groups of strata, since at that 

 time the Lower Silurian of Murchison had no well-defined base-line, 

 physical or zoological, while the Cambrian or protozoic of Sedgwick, as 

 distinguished from the Lower Silurian, was without a fauna. Even 

 the Lingula Davisii, which will presently be mentioned, was not dis- 

 covered till 1846, at which time the new organic types of Bohemia, 

 older than the Lower Llancleilo beds above described, were so peculiar 

 as to enable geologists from that time forth to identify by their means 

 alone in Scandinavia, Russia, Canada, and the United States, strata of 

 corresponding age. It was some years. before a sufficient number of 

 British fossils were found below the Lower Llandeilo beds to enable 

 the geologist to identify the different members of the Cambrian 

 group with their equivalents in Ireland and Scotland, and other 

 parts of Europe. If, therefore, M. Barrande had, in 1846, called the 

 fossiliferous rocks of his Etage C "Bohemian," that name would, 



* Trilobites de Bohenie, Leipsig, 1846. 



