144 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 25, 



Spirigerina I'eticularis (Bala to Devonian) . 



Lept(2na depressa (Bala to Carboniferous). 



Strophomena euglypha (Wenlock). 



Strophomena Pecten (Bala and Wenlock). 



Homalonotus Belphinocephalus (Wenlock). 



Cornulites serpularius (Wenlock and Ludlow). 

 Two conclusions seem to follow from such a list ; first, that the 

 fossil lists of the Presteign limestone (given by Mr. Davis), do not 

 prove it to be of the Wenlock age ; for by the same argument we 

 might identify the Wenlock and Woolhope limestones, although 

 actually separated from one another in the same section ; secondly, 

 that the Woolhope limestone might very properly have been called a 

 lower Wenlock limestone, and that it cannot, with propriety, be con- 

 sidered as the highest sub-group of the Caradoc sandstone. These 

 conclusions seem to be in accordance with the published views of 

 Professor Phillips. 



§ 3. Comparison of the three great groups of the Lake Moun- 

 tains, with the Cambrian and Silurian groups of North and South 

 Wales. 



I will first enumerate (in ascending order) the several groups into 

 which the whole Welsh series (Cambrian and Silurian) may, I think, 

 be conveniently subdivided ; and I may premise, that I consider all 

 the palseozoic rocks, from the lowest Cambrian to the highest Per- 

 mian, as one system — the primary or palaeozoic system. This primary 

 system admits of three great subdivisions ; viz. a lower subdivision, 

 including the Cambrian and Silurian series ; a middle, including the 

 Devonian series; and an upper, including the Carboniferous and 

 Permian series. These three subdivisions belong to one great sy sterna 

 naturce, the subordinate parts of which often pass one into another, 

 by almost insensible gradations ; although the species in the several 

 subdivisions and subordinate groups often entirely, or almost en- 

 tirely, change*. But the primary system, thus defined, differs 

 entirely from the systema natures of the secondary system ; and, in 

 like manner, the systema naturce of the secondary system differs 

 almost entirely from the systema natures of the tertiary system. 

 Lastly, we have the actual systema natures of the living world ; but 

 between the tertiary system and that of living nature no one has yet 

 drawn any intelligible line of demarcation. 



I do not pretend to answer a question, whether the primary, se- 

 condary, and tertiary systems may not, in progress of discovery, be 

 at length brought in a similar intimate relation ; neither do I discuss 

 a question respecting the expediency of any further subdivisions of 

 the secondary system. A good classification only represents the 

 actual condition of our knowledge ; and the following remarks relate 

 only to the classification of the subordinate groups of the lower pa- 

 laeozoic system, as above defined. To avoid all verbal ambiguity, or 



* This view of regarding all the Palaeozoic rocks as of one system is not new. 

 It has often been discussed in this Society ; and it was formally advanced by 

 myself in 1843. — Proceed. Geol. Soc. vol. iv, p. 223. 



