356 CAMBRIAN AND SILURIAN IN EUROPE. [XV. 



in this connection we are to understand only the Upper Cam- 

 brian or Bala group of Sedgwick, as appears from the express 

 statement of Murchison, who alludes to the Cambrian of Sedg- 

 wick as including all the older slaty rocks of Wales, and as 

 divided into three groups, but proceeds to say that in his 

 present work (the Silurian System) he shall notice only the 

 highest of these three. 



Since January, 1834, when Murchison first announced the 

 stratigraphical relations of the lower division of what he after- 

 wards called the Silurian system, the aspect of the case had 

 materially changed. This division was no longer underlaid, 

 both to the east in Shropshire and to the west in Wales, by a 

 great unfossiliferous series. His observations in the vicinity 

 of the Berwyn hills with Sedgwick in 1834, and the subse- 

 quently published statements of the latter, had shown that 

 this supposed older series was not without fossils ; but on the 

 contrary, in North Wales, at least, held a fauna identical with 

 that characterizing the Lower Silurian. Hence the assertion of 

 Murchison in his work on the Silurian System, in 1839, that it 

 was not possible to draw any line of demarcation between 

 them. The position was very embarrassing to the author of 

 the Silurian System, and, for the moment, not less so to the 

 discoverer of the Upper Cambrian series. Meanwhile, the 

 latter, as we have seen, in 1842 re-examined with Salter his 

 Upper Cambrian sections in North Wales, and satisfied him- 

 self of the correctness, both structurally and palaeontologically, 

 of his former determinations. Murchison, in his anniversary 

 address as President of the Geological Society in 1842, after 

 recounting, as we have already done, the history of the naming 

 by Sedgwick, in 1835, of the Cambrian series, which Murchi- 

 son supposed to underlie his Silurian system, proceeded as 

 follows : " Nothing precise was then known of the organic 

 contents of this lower or Cambrian system except that some of 

 the fossils contained in its upper members in certain promiin'iit 

 localities were published Lower Silurian species. Meanwhile, 

 l>y adi.ptiiig the word Cambrian, my friend and myself were 

 certain that whatever might prove to be its zoological distinc- 



