1865.] Jenkins on Strata identified by Organic Bemains. 629 



it appears to me that there is not sufficient difference between it 

 and the existing East Indian fauna to warrant any future " Post- 

 quaternary " geologist with our present principles, taking into 

 account the difference of latitude, and not giving any weight to 

 the doctrine I am advocating, in assigning it to any other than a 

 Miocene period. Therefore I believe that the time required for the 

 deposition of a formation several thousand feet in thickness, is not 

 necessarily greater than that required for the emigration of a fauna 

 to a great distance, when caused by a change of climate or a con- 

 siderable alteration in the physical features of the earth's surface. 



Professor Ramsay makes another objection that requires a few 

 words of explanation, as he considers it of importance. He remarks 

 that, " if the idea put by Professor Huxley be just, it appears to me 

 that in the piles of formations built up in Britain, on the Continent, 

 and in America, the chances are overwhelmingly strong, that in each 

 or in some one area there might be a recurrent fauna, which is not the 

 case. To this I attach great weight." * There are two answers to be 

 given to this objection : first, when the physical changes have not 

 been sufficiently great to expel the fauna completely, then we do get 

 an actual recurrence, of part of a fauna, at least ; secondly, that when 

 the physical changes have been very great, they must have occupied 

 so long a time and caused such an alteration in the conditions of 

 existence, that the species had to "flee for their lives." In the 

 " struggle for existence " that followed, under new and more or less 

 unfavourable circumstances, many were exterminated, and the majority 

 of the survivors so changed that they are now considered different 

 species from their ancestors. As I differ from Professor Eamsay in 

 the first part of my answer, I ought to prove my assertion. This 

 cannot be done better than by a quotation from his own Anniversary 

 Address to the Geological Society, for the following year ; it runs 

 thus, " The majority of the forms that passed upwards from the 

 Inferior Oolite limestone, seem to have fled the muddy bottom of 

 the Fuller's Earth sea, and to have returned to the same area,\ when 

 the later period of the Great Oolite began." J Here, therefore, Professor 

 Ramsay acknowledges the occurrence of a recurrent fauna. 



There is but one other phase of this question that I shall now 

 endeavour to discuss, namely, that if widely separated strata apparently 

 contemporaneous are not really so, it may be urged that it becomes 

 almost a farce to attempt to correlate distant deposits, unless we 

 have some golden rule with which to find out their difference in age. 

 Mr. Salter has neatly enunciated this kind of scruple, by saying 

 that "it is hard to have to question every conclusion as it arises," § 

 and doubtless it is a very hard thing at first ; but as all men of 

 science love, or ought to love, truth more than apparent symmetry, 

 they will soon get over this feeling, and in the meantime we must 

 seek for a remedy to assist them in doing so. Such a remedy has 

 been proposed by Professor Huxley, in his Anniversary Address 



* Op. cit., p. 26. f The italics arc miue. 



\ Address Geol. Soc, 1864, p. 26. § 'Geol. Mag.,' vol. i. p. 5. 



