2 3 8 



SCIENTIFIC NEWS. 



[Sept. 7, i? 



plants were pushed far to the south of their present habitat. In 

 consequence of this Mr. Gardner concludes that " it is useless to 

 seek in the Arctic regions for Eocene floras as we know them in 

 our latitudes, for during the Tertiary Period the climatic conditions 

 of the earth did not permit their growth there. Arctic fossil floras 

 of temperate and therefore Meiocene aspect are in all probability of 

 Eocene age, and what has been recognised in them as a newer or 

 Meiocene facies is due to their having been first studied in Europe 

 in latitudes which only became fitted for them in Meiocene times. 

 When stratigraphical evidence is absent or inconclusive, this un- 

 expected persistence of plant types or species throughout the 

 Tertiaries should be remembered, and the degrees of latitude in 

 which they are fcund should be well considered before conclusions 

 are published respecting their relative age." 



This view is consistent with that held by the leaders in botany, 

 Hooker, Dyer, Saporta, Dawson, and Asa Gray — whose recent loss 

 we so deeply deplore— that the North Polar region is the centre of 

 dispersal, from which the Dicotyledons spread over the Northern 

 Hemisphere. If it be true — and I, for one, am prepared to accept 

 it — it will follow that for the co-ordination of the subdivisions of 

 the Tertiary strata in various parts of the world the plants are un- 

 certain guides, as they have been shown to be in the case of the 

 Primary and Secondary rocks. In all cases where there is a clash 

 of evidence, such as in the Laramie lignites, in which a Tertiary 

 flora is associated with a Cretaceous fauna, the verdict in my 

 opinion must go to the fauna. They are probably of the same geo- 

 logical age as the deposit at Aix-la-Chapelle. 



I would remark further, before we leave the floras behind us, that 

 the migration of new forms of plants into Europe and America 

 took place before the arrival of the higher types in the fauna, after 

 the break-up of the land at the close of the Carboniferous period, 

 and after the great change in geography at the close of the Neoco- 

 mian. The Secondary plants preceded the Secondary vertebrates 

 by the length of time necessary for the deposit of the Permian rocks, 

 and the Tertiary plants preceded the Tertiary vertebrates by the 

 whole period of the Upper Cretaceous. 



Let us now turn to the fauna. 



Professor Huxley, in one of his many addresses which have left 

 their mark upon our science, has called attention to the persistence 

 of types revealed by the study of Palaeontology, or, to p n it in other 

 words, to the singularly little charge which the ordinal groups of 

 life have undergone since the appearance of life on the earth. The 

 species, genera, and families present an almost endless series of 

 changes, but the existing orders are for the most part sufficiently 

 wide, and include the vast series of fossils without the necessity of 

 framing new divisions for their reception. The number of these 

 extinct orders is not equally distributed through the animal king- 

 dom. Taking the total number of orders at 108, the number of 

 extinct orders in the Invertebrata amounts only to 6 out of 88, or 

 about 7 per cent., while in the Vertebrates it is not less than i2out 

 of 40, or 30 per cent. These figures imply that the amount of 

 ordinal change in the fossil Vertebrates stands to that in the Inverte- 

 brata in the ratio of 30 to 7. This disproportion becomes still more 

 marked when we take into account that the former had less time for 

 variation than the latter, which had the start by the Cambrian and 

 Oidovicean Periods. It follows also that as a whole thty have 

 changed faster. 



The distiibution of the extinct orders in the animal kingdom, 

 tak;n along with their distribution in the rocks, proves further that 

 some types have varied more than others, and at various places in 

 the geological record. In the Protozoa, Porifera, and Vermes there 

 are no extinct orders ; among the Ccelenterates or.e : the Rugosa ; 

 in the Echinodermata three : Cystideans, Edriasterida, and 

 Blastoidea ; in the Arthropoda two : the Trilobita and Eurypterida. 

 All these, with the solitary exception of the obscure order Rugosa, 

 are found only in the Primary rocks. Among the Pisces there are 

 none ; in the Amphibia one ; the Labyrinthodonts ranging from 

 the Carboniferous to the Triassic Age. Among the Reptilia there 

 are at least six of Secondary age : Plesiosauria, Ichthyosauria, 

 Dicynodontia, Pterosauria, Thetiodontia, Deinosauria; in theAves 

 two : the Saururae and Odontornithes, also Secondary. In the 

 Mammalia the Amblypoda, Tillodontia, Condylarthra, and Toxo- 

 dontia represent the extinct orders — the three first Early Tertiary, 

 and the last Pleistocene. It is clear therefore that, while the maxi- 

 mum amount of ordinal variation is presented by the Secondary 

 Reptilia and Aves, all the extinct orders in the Tertiary are Mam- 

 malian. 



If we turn from the extinct orders to the extinct species, it will 

 also be found that the maximum amount of variation is presented by 

 the plants, and all the animals, excepting the Mammalia, in the 

 Primary and Secondary Periods. 



The general impression left upon my mind by these facts is that, 

 while all the rest of the animal kingdom had ceased to present im- 



portant modifications at the close of the Secondary Period, the 

 Mammalia, which presented no great changes in the Secondary 

 rocks, were, to quote a happy phrase of Professor Gaudry, " en 

 pleine evolution " in the Tertiary Age. And when, further, the 

 singular perfection of the record allows us to trace the successive and 

 gradual modifications of the Mammalian types from the Eocene to 

 the close of the Pleistocene Age, it is obvious that they can be used 

 to mark subdivisions of the Tertiary Period, in the same way as the 

 reigns of kings are used to mark periods in human history. In my 

 opinion they mark the geological horizon with greater precision than 

 the remains of the lower members of the animal kingdom, and in 

 cases such as that of Pikermi, where typical Meiocene forms, such 

 as Deinotheria, are found in a stratum above an assemblage of 

 marine shells of Pleiocene age, it seems to me that the Mammalia 

 are of greater value in classification than the Mollusca, some of the 

 species of which have been living from the Eocene down to the 

 present day. 



Yet another important principle must be noted. The fossils are 

 to be viewed in relation to those forms now living in their respective 

 geographical regions. The depths of the ocean have been where 

 they are now since the earliest geological time;, although continued 

 geographical changes have been going on at their margins. In other 

 words, geographical provinces must have existed even in the earlier 

 geological periods, although there is reason to believe that they did 

 not differ so much from each other a; at the present day. It follows 

 from this that the only just standard for compirison in dealing with 

 the fossils, and especially of the later rocks, is that which is offered 

 by the fauna and flora of the geographical province in which they 

 are found. The non-recognition of this principle has led to serious 

 confusion. The fauna, for example, of the Upper Sivalik Formation 

 has been very generally viewed from the European standpoint an-1 

 placed in the Meiocene, while, judged by the standpoint of India, it 

 is really Pleiocene. A similar confusion has followed from taking 

 the Meiocene flora of Switzerland as a standard for the Tertiary 

 flora of the whole of the Northern Hemisphere. 



It now remains for us to see how th-;-e principles may b^ applied 

 to the co-ordination of Tertiary strata in various parts of the world. 

 In 1880 I proposed a classification of the European Tertiaries, in 

 which, apart from the special characteristic fossils of each group, 

 stress was laid on the gradual approximation of various groups to 

 the living Mammalia. The defini.ions are the following: — 



Characteristics. 

 Extinct orders. 

 Living orders and fam'lies. 

 No living genera. 



Divisions. 



1. Eocene, or that in which 

 the higher Mammalia (Eutheria) 

 now on the earth were repre- 

 sented by allied forms belong- 

 ing to existing orders and fami- 

 lies. 



CXigocene. 



2. Meiocene, in which the 

 alliance between fossil and liv- 

 ing Mammals is closer than be- 

 fore. 



3. Pleiocene, in which liv- 

 ing species of Mammals appear. 



4. Pleistocene, in which liv- 

 ing species of Mammals pre- 

 ponderate. 



5. Prehistoric, or that period 

 outside history in which Man 

 has multiplied exceedingly on 

 the earth and introduced the 

 domestic animals. 



6. Historic, in which the 

 events are recorded in history. 



These definitions are of more than European significance. The 

 researches of Leidy, Marsh, and Cope prove that they apply equally 

 to the Tertiary strata of North America. 



It maybe objected to the Prehistoric and Historic divisions of the 

 Tertiary perioi that neither the one nor the other properly fall 

 within the domain of geology. It will, however, be found that in 

 tracing the fauna and flora from the Eocene downwards to the 

 present day there is no break which renders it possible to stop short 

 at the close of the Pleistocene. The living plants and animals were 

 in existence in the Pleistocene age in every part of the world which 

 has been investigated. The European mollusca were in Europe in 

 the Pleiocene age. The only difference between the Pleistocene 

 fauna, on the one hand, and the Prehistoric, on the other, consists in 

 the extinction of certain of the mammalia at the close of the 

 Pleistocene age in the Old and New Worlds, and in Australia. 

 The Prehistoric fauna in Europe is also characterised by the intro- 

 duction of the ancestors of the present domestic animals, some of 



Living genera. 

 No living species. 



Living species few. 

 Extinct species predominant. 

 Living species abundant. 

 Extinct species present. 

 Man present. 

 Man abundant. 

 Domestic animals present. 

 Wild Mammals in retreat. 

 One extinct Mammal. 



Records. 



