XV.] CAMBRIAN AND SILURIAN IN EUROPE. 355 



the first two in his Silurian system, and the last deep down in 

 the Upper Cambrian; and consequently was aware that on 

 palaBontological grounds it was impossible to separate the lower 

 portion of Silurian system from the Upper Cambrian of Sedg- 

 wick. (These names are here used for convenience, 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 common to the Lower Silurian system." This was 

 again insisted upon by him in 1838 and 1841. (Proc. Geol. 

 Soc., II. 679 ; III. 548.) It was not until 1840 that Bowman 

 announced the same conclusion, which was reiterated by 

 Sharpe in 1842. (Ramsay, Mem. Geological Survey, III. Part 

 II. p. 6.) 



In 1839, Murchison published his Silurian System, dedi- 

 cated to Sedgwick, a magnificent work in two volumes quarto, 

 with a separate map, numerous sections, and figures of fossils. 

 The succession of the Silurian rocks, as there given, was pre- 

 cisely that already set forth by the author in 1834, and again 

 in 1835 ; being, in descending order, Ludlow and Wenlock, 

 constituting the Upper Silurian, and Caradoc and Llandeilo 

 (including the Lower Llandeilo beds or Stiper-stones), the 

 Lower Silurian. These are underlaid by the Cambrian rocks, 

 into which the Llandeilo was said to offer a transition marked 

 by beds of passage. Murchison, in fact, declared that it was 

 impossible to draw any line of separation, either lithological, 

 zoological, or stratigraphical, between the base of the Silurian 

 beds (Llandeilo) and the upper portion of the Cambrian, the 

 whole forming, according to him, in Caermarthenshire, one 

 continuous and conformable series from the Cambrian to the 

 Ludlow. (Silurian System, pages 256, 258.) By Cambrian 



