388 !- P- BLAKE AND W. H. HUDLESTON ON 



Conclusions. 



The descriptions we have given of the actual development of 

 Corallian rocks in England shows how inappropriate is the term 

 " Coral Rag " as a designation for the whole, any thing that 

 could be lithologically called by that name forming but a very 

 small part of the series. " Coralline Oolite " is an equally 

 inappropriate term when separated from the rock which it 

 properly describes. As, however, the great interest which at- 

 taches to the series of rocks which is the subject of this memoir 

 centres in the fact of their containing the last development of coral- 

 reefs within the British area, which is now too cold for their 

 formation, they may be appropriately known under the name that 

 we have used, " Corallian." We see, too, that we have not been 

 describing a set of rocks under this designation that are sharply 

 marked off above and below, but rather the gradual changes that 

 took place during a certain epoch in the earth's history, and the 

 results to which they led. "We have seen how the lower beds are 

 still markedly Oxfordian in the character of their fauna, and how 

 gradually the peculiar forms suited for connexion with coral 

 growths were introduced, and how, before they had died out, Kim- 

 meridgian forms became their companions, and ultimately sup- 

 planted them. The earth's history is not the disjunctive story of a 

 dynasty, but the continuous one of a nation. 



Although it is true that the series of changes above indicated 

 were generally introduced by the deposit of calcareous sands which 

 have become to a certain extent grits, that the succeeding deposits, 

 whether connected with corals or not, are limestones, frequently 

 oolitic, and that in those cases where we see the return to the pelagic 

 conditions of the Kimmeridgian epoch it is marked by a deposit of 

 calcareous grits, we see that it is erroneous, and in the case of 

 Yorkshire impossible, to call these simply the Lower Calcareous 

 Grit, Coralline Oolite, and Upper Calcareous Grit, as we should 

 thereby correlate all the limestones together, and the same with the 

 other portions. 



In the extreme north and the extreme south the series of changes 

 were much more complex, and the development at a maximum ; yet 

 the characters of the several series differ widely, and in the inland 

 counties the development reaches its minimum, and really has many 

 of the better-developed portions not represented at all. 



These facts show that a correlation in time is impossible ; for 

 where the Coral Rag rests immediately on the Lower Calcareous 

 Grit, the latter may represent in time the whole of the vast deposits 

 elsewhere forming the basis of the Rag, or this latter trslj not have 

 been elsewhere contemporaneous. 



The character of the deposits, wherever we have studied them, has 

 been that of lenticular masses of an elliptical shape, thinning out 

 in all directions, but with diameters of very unequal length. In 

 this way it happens that beds of the same character and position 

 are not parts of a widespread whole, but are the results of similar 



