THK CAMBRIAN SYSTEM 



71 



into it, till the Lower Silurian came to include the whole of the 

 rocks (below the Upper Silurian) in which any fossils had been 

 found. This was obviously unfair and unscientific, since the so- 

 called Lower Silurian was in reality a part of Sedgwick's Cambrian 

 Series, the delineation of which by Sedgwick was accurate ft"d 

 complete. Still it was done, and the name Lower Silurian was 

 generally adopted both in England and abroad. 



The fact is, Sedgwick and Murchison both described more than 

 one system of rocks, and each included two systems under one 

 name. Sedgwick had clearly a right to call one system Cambrian 

 and Murchison to call one Silurian, but there is really a thin! 

 intermediate system, containing the second great fauna in the life- 

 history of the globe, and to this neither geologist had a distinct 

 claim. For this intermediate system Professor Lapworth proposed 

 the name Ordovician (from the tribe of the Ordovices who inhabited 

 North Wales), remarking, 3 " That so long as present systems of 

 nomenclature survive, nothing can disturb the application of the 

 title Cambrian to the rocks of the ' Primordial Series,' and that of 

 Silurian to the strata of the ' Third Fauna.' It is vastly different, 

 however, with the intermediate series, which has been the object 

 of incessant disputes from the day it was recognised until now." 

 This proposal has met with very general acceptance, and has recently 

 been adopted by the Geological Survey. 



The following table shows the original arrangements of Sedgwick 

 and Murchison, that formerly used by the Geological Survey, and 

 lastly the one which is now in general use. 



Classification of the Cambrian System. Since the time of 

 Sedgwick and Murchison the Cambrian rocks have been investigated 

 much more completely, and fossils have been found at various horiions 

 down to the very base of the system. Fresh subdivisions have 

 been established and new names introduced into the nomenclature, 

 A Menevian Group lias been separated from the Lingula flag*, and 



