230 GEOLOGICAL DISTEIBUTION. 



succeeded one which, when the two are in superposition, all over 

 the world (as far as we are aware) indicates precedence in creation 

 or origination, and never one that can be shown to be of a later 

 birth ? Surely these- peculiar circumstances cannot be accounted 

 for on the doctrine of a fortuitous migration. And it certainly can- 

 not be supposed that, through a process of transmutation or develop- 

 ment, depending upon the evolutionary forces, a fauna with an 

 early-life facies will, in each case, at the point of its arrest have 

 assumed the character of the later-day fauna which belongs to that 

 position. Therefore, it appears inconceivable that a very great 

 period of time should have intervened between the deposition of the 

 fauna of one great geological epoch at one locality and that of the 

 same or similar fauna at another locality distantly removed from the 

 first. In other words, the migrations, for such must imdoubtedly 

 have been the means of the distant propagation of identical or very 

 closely related life-forms (unless we admit the seemingly untenable 

 hypothesis that equivalent life-forms may have been very largely 

 developed from independent and very dissimilar lines of ancestry), 

 must have been much more rapidly performed than has generally 

 been admitted by naturalists. The facts of geology and paleontol- 

 ogy are decidedly antagonistic to any such broad contemporaneity 

 or non-contemporaneity as has been assumed by Professor Huxley ; 

 and their careful consideration will probably cause geologists to 

 demur to the statement that " all competent authorities will prob- 

 ably assent to the proposition that physical geology does not enable 

 us in any way to reply to this question : "Were the British Cretaceous 

 rocks deposited at the same time as those of India, or are they a 

 million of years younger or a million of years older ? " 



But what applies to the broader divisions of the geological scale 

 also applies to the minor divisions. Thus, the subordinate groups 

 of a formation are almost as definitely marked off in the same order, 

 the world over, as are the formations themselves. After breaks in 

 formations the appearance of characteristic fossils is largely the 

 same, whereas, on the theory of synchronism of distinct faunas, 

 such a succession of forms would certainly not be constant. Taking 

 the facts in their entirety, the conclusion appears irresistible that 

 formations characterised by the same or very nearly related faunas, 

 in widely separated regions, belonged, in very moderate limits, to 

 approximately the same actual age, and were practically synchronous 



