22 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



W. 60°, leans over the lower carboniferous shales, A little to the 

 north of this spot, the limestone and shale are seen in their natural 

 position, but, as their strike differs considerably from that at Pepin- 

 ster, they could not be shown in the same section. The accurate 

 working out of a country in which such disturbances are of common 

 occurrence has placed M. Dumont's name in the first rank of Euro- 

 pean geologists. 



The difficulty of arranging the rocks of Devon and Cornwall seems 

 mainly due to the existence of faults of the same character as those 

 above described, accompanied with flexures similar to those of the 

 Belgian coal-field. In those counties masses of rock of difl'erent ages 

 are brought into contact along east and west lines of fault ; and the 

 prevalence of a southerly dip gives them an appearance of conform- 

 able superposition, which has led to most erroneous and contradictory 

 views of the relative ages of the different masses on the part of dif- 

 ferent observers. 



Let us now compare the divisions of M. Dumont's Table with our 

 English formations. The Systhne hoiiillier answers to the Coal- 

 measures of our midland counties, and to the Upper Coal Series of 

 Northumberland and Scotland. 



The Systhne condrusien corresponds to our Carboniferous Series ; — 

 the upper calcareous division, including the Vise limestone, crowded 

 with large Producti, &c., may be compared to the limestone of Mat- 

 lock and Bristol. The middle division of grey psammite with some 

 beds of anthracite answers to the arenaceous series between our Upper 

 and Lower Carboniferous limestones, on which level coal is worked 

 both in the north of England and in Scotland. The lowest division, 

 of grey and carbonaceous shales, dark limestones and iron-ore, is best 

 matched in Northumberland and in the Lothians. "We saw the 

 upper part of this division in the great quarries round Tournay, 

 where the following beds are laid open : — 



Alternations of dark shale, containing Spirifer, Cyathophyllum, 

 mitratum, &c., with clay-iron-stone. 



Dark limestone. 



Black shales, alternating with some thin beds of limestone ; the 

 shales full of corals and small shells, among which PleurotomaricB 

 are especially abundant. 



The lower limestone shales of Northumberland and of the Scotch 

 coal-fields contain an assemblage of shells much resembling those of 

 Tournay, and I am disposed to place in the same division the whole 

 of the Culm-series of Devonshire, together with the underlying fos- 

 sihferous beds of Pilton and Barnstaple (and perhaps Marwood) in 

 North Devon, and of Tintagel and South Petherwin in the South, 

 the organic contents of which agree much more nearly with Carboni- 

 ferous, than with Devonian species. In 1843 I urged Mr. Morris to 

 separate this group in his Catalogue from the Devonian system*, and 

 the opinion of many palseontologists has gradually come round to the 

 same view. 



The Systems eifelien of M, Dumont is formed of three distinct 

 * See Catalogue of British Fossils, 1843, Introduction, page x, Note. 



