354 CAMBRIAN AND SILURIAN IN EUROPE. [XV. 



had been given to these respectively, Sedgwick and Murchison 

 visited together the principal sections of these rocks from Caer- 

 marthenshire to Denbighshire. The greater part of this region 

 was then unknown to Sedgwick, but had been already studied 

 by Murchison, who interpreted the sections to his companion 

 in conformity with the scheme already given ; according to 

 which the beds of the Llandeilo were underlaid by the slaty 

 rocks which appear along their northwestern border. When, 

 however, they entered the region which had already been ex- 

 amined by Sedgwick, and reached the section on the east side 

 of the Berwyns, the fossiliferous beds of Meifod were at once 

 pronounced by Murchison to be typical Caradoc, while others 

 in the vicinity were regarded as Llandeilo. The beds of Mei- 

 fod had, on palseontological grounds, been by Sedgwick identi- 

 fied with those of Glyn Ceirog, which are seen to be immedi- 

 ately overlaid by Wenlock rocks. These determinations of 

 Murchison were, as Sedgwick tells us, accepted by him with 

 great reluctance, inasmuch as they involved the upper part of 

 his Cambrian section in most perplexing difficulties. AYln-n 

 however, they crossed together the Berwyn chain to Bala, the 

 limestones in this locality were found to contain fossils nearly 

 agreeing with those of the so-called Caradoc of Meifod. The 

 examination of the section here presented showed, however, 

 that these limestones are overlaid by a series of several thou- 

 sand feet of strata, bearing no resemblance either in fossils or 

 in physical characters to the Wenlock formation, which over- 

 lies the Caradoc beds of Glyn Ceirog. This series, was, tlu-iv- 

 fore, by Murchison supposed to be identical with the rocks 

 which, in South Wales, he had placed beneath the Llandeilo, 

 and he expressly declared that the Bala group could not be 

 brought within the limits of his Silurian system. It may here 

 be added that in 1842 Sedgwick re-examined this region, 

 accompanied by that skilled paleontologist, Salter, confirming 

 the accuracy of his former sections, and showing, moreover, by 

 the evidence of fossils that the beds of Meifod, Glyn Ceirog, 

 and Bala are very nearly on one parallel. Yet, with the evi- 

 dence of the fossils before him, Murchison, in 1834, placed 



