i 24. the cumbrian or schistose strata. 797 



The Cumbrian System. 



(Commencing icith the uppermost.) 



1. Upper slate of Kendal. — Greenish grey flagstones, grits, and 



slates, with Upper Ludlow fossils. 



2. Ireleth slates. — Coarse slates, flags, and grits; with calcareous 



slates and limestones : containing Lower Ludlow fossils. 



3. Coniston grits and flagstones : with Upper Silurian species of 



fossils. 



4. Coniston limestone and slate, with Lower Silurian fossils. 



As no assemblage of organic remains distinct from that 

 of the Silurian system has been discovered, a zoological 

 line of separation cannot be drawn between the Silurian 

 and Cambrian deposits ; and Sir E. Murchison now classes 

 the whole of the fossiliferous slates with the Lower Silurian,; 

 employing the term Cumbrian to designate certain schistose 

 rocks in the Lake districts, which are destitute of organic 

 remains, and underlie the fossiliferous beds in an uncon- 

 formable position. On the other hand, Professor Sedgwick 

 considers the zoological characters both of the Cambrian 

 and Cumbrian groups, as sufficiently distinct from the 

 Silurian, to warrant their establishment as a separate sys- 

 tem, apart from their mineralogical structure. The dis- 

 covery of other peculiar types of organic remains in the 

 slate rocks, can alone determine the propriety of their 

 separation.* Without presuming to decide upon this ques- 

 tion, I shall endeavour to avoid confusion, by using the term 

 Cumbrian to designate the lowermost and most ancient 

 slate rocks, in which very few, if any, organic remains have 

 been detected, and those only in the uppermost zone ; and 

 restrict the name Cambrian to the slate rocks of North 

 Wales. 



* The arguments of these eminent geologists in support of their 

 respective opinions, are fully stated in Vol. III. part i. of the Quarterly 

 Journal of the Geological Society, by Professor Sedgwick, pp. 133 — 

 164 ; and by Sir R. Murchison, pp. 165—179. 



