338 GEOLOGICAL DISTEIBUTIOK. 



Pushing his conclusion to what appeared to be its furthest 

 legitimate point, Professor Huxley deduced therefrom two impor- 

 tant considerations: 1. That formations exhibiting the same faunal 

 facias may belong to two or more very distinct periods of the geo- 

 logical scale as now recognised ; and, conversely, formations whose 

 faunal elements are quite distinct may be absolutely contcmjiorane- 

 ous; e. g., "For anything that geology or paleontology is able to 

 show to the contrary, a Devonian fauna and flora in the British 

 Islands may have been contemporaneous with Silurian life in North 

 America, and with a Carboniferous fauna and flora in Africa." 2. 

 That, granting this disparity of age between closely-related faunas, 

 all evidence as to the uniformity of physical conditions over the 

 surface of the earth during the same geological period (i. «., the 

 periods of the geological scale), as would appear to be indicated by 

 the similarity of the fossil remains belonging to that period, falls 

 to the ground. " Geographical provinces and zones may have been 

 as distinctly marked in the Paleozoic epoch as at present, and those 

 seemingly sudden appearances of now genera and species, which 

 we ascribe to new creation, may be simple results of migration. " 



These views are still held by a very large body of geologists. 

 But it can be readily shown by a logical deduction that at least one 

 of the conclusions amved at (1) is, almost certainly, erroneous; 

 and that the second, based upon this one, derives no conflrmation 

 from the supposed facts. If, as is contended, several distinct 

 faunas — i. e., faunas characteristic of distinct geological epochs — 

 may have existed contemporaneously, then evidences of inversion 

 in the order of deposit ought to be common, or, at any rate, they 

 ought to be indicated somewhere, since it can scarcely be conceived 

 that animals everywhere would have observed the same order or 

 direction in their migrations. Given the possible equivalence in 

 age, as is argued, of the Silurian fauna of North America with the 

 Devonian of the British Isles and the Carboniferous of Africa, or 

 any similar arrangement, why has it never happened that when 

 migration, necessitated by alterations in the physical conditions of 

 the environs, commenced, a fauna with an earlier facies has been 

 imposed upon a later one, as the Devonian of Britain upon the 

 Carboniferous of Africa, or the American Silurian upon the British 

 Devonian ? Or, for that matter, the American Silurian might have 

 just as well been made to succeed the African Carboniferous. 



