older Deposits of the North of Germany and Belgium. 233 



Westphalia, being extremely prominent at Arnsberg (the capital of the eastern 

 portion of the province), which stands upon the black limestone and hiesel schiefer. 



Fig. 1. 



Section near Arnsberg. 



N. and by W. K < « S. and by E. 



<= d 



Sandstone and schists. Black limestone (carboniferous). Sandstone and schists, 



with small plants. Kiesel schiefer. with small plants. 



6+ of Map. 



This limestone is for the most part of a dull black colour, is extremely carbonaceous, argillaceous, and 

 fetid, and is usually traversed by many veins of white calc-spar. In mineral characters it is so nearly 

 identical with the black culm limestone of Devonshire, that the description of the one rock might almost 

 serve for that of the other. It is not, however, merely in lithological structure, but still further in 

 imbedded fossils, that this limestone is placed in parallel with that of Bideford, Bampton, Oakhampton, 

 and Launceston (see map of Devon, Geol. Trans, vol. v. PI. L.), being charged with Goniatites and 

 PosidonicB, which two genera are in Westphalia, as in Devonshire, by far the most abundant fossils of 

 the deposit. The Posidonia Becheri of Devonshire (Geol. Trans, vol. v. PI. LII. figs. 2 and 3) occurs 

 both in this part of Westphalia and in Nassau, and we are unable to distinguish one of the flattened 

 Goniatites of the one country from a Goniatite of the other. The " kiesel schiefer" and black limestone 

 of Eastern Westphalia must, we conceive, represent the ordinary carboniferous limestone of Ratingen, 

 notwithstanding a considerable difference in their respective fossils ; because the one is a continuation 

 of the other, and occupies precisely the same relative position in the series, as is proved by many trans- 

 verse sections. 



In confirmation of this view, we may be permitted to remark, that the mineral characters of no 

 one formation are uniformly persistent over large areas. That sandstone may graduate into limestone 

 and limestone into shale (or vice versa), and that the leading members of a deposit may be either 

 suppressed or entirely changed, are facts known to every geologist. It is equally well known that, with 

 every change in the lithological composition of a rock, there is often a corresponding variation in its organic 

 contents. Observations have often proved this fact, and it might indeed have been inferred from the 

 known conditions of animal life*. 



In tracing the course of the mountain limestone from Ratingen eastwards, we have remarked that the 

 dominant character was rapidly lost, that chert and black carbonaceous matter began to prevail in the 

 place of the thick, grey calcareous beds. How natural is it therefore to expect, that so great a change in 

 the marine sediment must have produced a great change in the forms of animal life — that a change of 

 conditions should have produced some corresponding change of species ! The zoological distinction of 

 two distant portions of the same band of rocks is, however, often more apparent than real, and the con- 

 necting links are generally to be traced if observations be accurate and long continued. In the strata 

 under review, though the large Productce and corals of Ratingen are wanting, yet Goniatites of certain 

 forms, which are among the most distinguishing fossils of the lower carboniferous rocks, are common. 



* This fact has been dwelt upon by Mr. De la Beche in his Survey of Devonshire and Cornwall. 

 The group of fossils in the oolitic series of Yorkshire may be quoted as an example in point; and it de- 

 serves remark, that when any part of that series (for example, the coral rag of Filey) approaches the 

 known types in Somersetshire or Wiltshire, the accompanying group of fossils also approaches that of 

 the corresponding formation in our south-western counties. 



