No. 3.] HUNT — ON CAMBRIAN AND SILURIAN. 285 



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 Meifod had, on paleontological grounds, been by 

 Sedgwick identified with those of Glyn Ceirog, which are seen to 

 be immediately overlaid by Wenlock rocks. These determina- 

 tions of Murchison were, as Sedgwick tells us, accepted by him 

 with great reluctance, inasmuch as they involved the upper part 

 of his Cumbrian section in most perplexing difficulties. When 

 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 thousand 

 feet of strata bearing no resemblance either in fossils or in 

 physical characters to the Wenlock formation which overlies the 

 Caradoc beds of Glyn Ceirog. This series was, therefore, 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, confii-ming 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 evidence of the fossils before him, 

 Murchison, in 1834, placed the first two in his Silurian system, 

 and the last deep down in the Upper Cambrian ; and consequently 

 was aware that on paleontological grounds it was impossible to 

 separate the lower portion of his Silurian system from the Upper 

 Cambrian of Sedgwick. (These names are here used for con- 

 venience; although we are speaking of a time when they had not 

 been applied to designate the rocks in question.) 



This fact was repeatedly insisted upon by Sedgwick, who, in the 

 Syllabus of his Cambridge lectures, published very early in 1837, 

 enumerated the principal genera and species of Upper Cambrian 

 fossils, many of which were by him declared to be the same with 

 those of the Lower Silurian rocks of Murchison. Again, in 

 enumerating in the same Syllabus the characteristic species of the 

 Bala limestone, it is added by Sedgwick : " all of which are com- 

 mon to the Lower Silurian system." This was again insisted 



