CONTEMPORANEITY OF STRATA. 21 



the view that the close of the period was marked by a sudden 

 and universal extinction and destruction of the characteristic 

 Cretaceous forms of life, there is only one other view which 

 we can take. Confining our attention solely to those seas of the 

 period of which alone we know enough for safe reasoning, 

 we know that the close of the Cretaceous period in Europe 

 was accompanied, or rather caused, by an upheaval of the 

 Cretaceous area, and an obliteration of the Cretaceous sea. 

 This upheaval was, of course, effected with extreme slowness, 

 or, at any rate, not suddenly, and it must have completely 

 changed the life-conditions or "environment" of the animals 

 which swarmed in the Cretaceous seas. Some of these would 

 doubtless be unable to accommodate themselves to their 

 altered surroundings, and would simply die out. Others, we 

 may presume, would migrate to some more favourable area, 

 and some of these might accomplish their migration without 

 undergoing any change. Most, however, of the forms which 

 migrated, in the process of migration, and by reason of coming 

 into contact with strange neighbours and untried conditions, 

 would probably undergo more or less modification. Ulti- 

 mately, therefore, many characteristic Cretaceous forms might 

 be transferred to some sea far distant from their original home. 

 Not only so, but some of the transferred species might have 

 suffered so much modification that they would no longer be 

 regarded as specifically identical Avith the original Cretaceous 

 forms, but would be looked upon simply as allied or " repre- 

 sentative " species, though really the lineal descendants of the 

 animals of the Chalk. 



It is perfectly clear that the process of rock - deposition 

 which was going on in Europe towards the close of the 

 Cretaceous period was not, and could not be, abolished by 

 the elevation of the European area, and the obliteration of the 

 Cretaceous sea, but was simply transferred to some other area. 

 In this particular case, we do not happen to know where the 

 new area of deposition may have been. It is quite certain, 

 however, that in whatever area the Cretaceous animals took 

 refuge, there rocks must have been deposited in course of 

 time, as they are in all seas, though it does not in the least 

 follow that the rocks of this new area should have the smallest 

 likeness in mineral composition to the Cretaceous sediments. 

 If we should at any time discover these rocks, it may pretty 

 safely be predicted what we should find in them in the way of 

 fossils. We should find, namely, some Cretaceous species, 

 probably unchanged ; with these there would be forms allied 

 to the Cretaceous species, but differing from them to a greater 



