THE CORALLIAN ROCKS OF ENGLAND. 391 



We pass finally to a brief consideration of the physical causes 

 concerned in the formation of these rocks. In the Yorkshire area 

 we have a maximum of calcareous deposits ; and here too we obtain 

 the finest reefs. The higher latitude of this county did not out- 

 match the influence of favourable conditions for their growth 

 through a considerable period of time. We note, however, that on 

 the east coast of Scotland Mr. Judd has not recorded a single coral 

 from beds of this period, though the conditions there do not appear 

 to have been unfavourable ; so that the northern limit is soon 

 reached. The disposition of the Corallian beds round the vale of 

 Pickering, and some peculiarities of their stratigraphy in relation to 

 tremendous faults by which they are affected, render it difficult to 

 indicate precisely the source of the deposits ; most probably the 

 sediment, at least, came from the north and west. 



In the extreme south, though the warmth would encourage coral- 

 growth, the great preponderance of argillaceous conditions must 

 have choked them, these clay masses, as all the others, having come 

 from land to the south and west. 



In the North-Dorset district we have again abundance of cal- 

 careous matter, and the reefs were probably not far to the west ; 

 but here some other causes prevented their growing on the spot. 



In the central range the huge sandbanks appear to have given 

 support first to some shell-beds at different ages, and then to have 

 been very favourable to coral-growth. 



In every v case, however, we have, in the very fact of the great 

 variety manifest in the deposits, a proof that we are not dealing 

 with pelagic conditions, but are under the influence of neighbouring 

 lands or shallow water ; and the beds we see are a faithful record, 

 not of permanent conditions, but of continual changes, favourable 

 or otherwise to the growth of coral. 



But one great change has passed over the country since then : it 

 has become too cold for corals at all ; so that we here see for the 

 last time the formation of a reef, the structure of which is laid 

 bare before us ; and very beautiful it is, especially where it has 

 been undisturbed. The influence of these rocks is not unfelt 

 even in the great clay deposits in the centre of England, where a 

 middle division has been indicated, characterized, as we have seen, 

 by some essentially Corallian fossils ; and we doubt not that a 

 careful examination of these clays would show a still closer con- 

 nexion. 



Descriptions and Notes on the Fossils. 



Belemnites. 



Between the stout B. abbreviatus of the lower beds and the much 

 narrower B. nitklus of the uppermost, are some which form, perhaps, 

 the passage between them, being of intermediate age as well as 

 shape. We have not thought it desirable, however, to give them 

 distinct names at present. 



