44° 



NA TURE 



{Sept. 4, ii 



SECTION C 



Opening Address by W. T. Blanford, F.R.S., Sec.G.S., 

 F.R.G.S., President of the Section 



In commencing an address to the Geological Section of the 

 British Association on the first occasion on which that body has 

 met outside of the British Islands I feel much difficulty. Amongst 

 the eminent geologists who have filled the post which you have 

 done me the honour of calling upon me to occupy for the present 

 year there are several who would have been able, from their 

 knowledge of both European and American geology, to treat 

 with authority of the many points of interest elicited by com- 

 parison of geological phenomena on opposite sides of the Atlantic 

 Ocean. My own experience has been chiefly derived from the 

 distant continent of Asia, and I have not that intimate acquaint- 

 ance with the geology of Europe, nor that knowledge of the 

 progress of geological research in America, which would justify 

 my entering upon any comparison of the two continents. It has, 

 however, occurred to me that, amongst the questions of wide im- 

 portance connected with the correlation of strata in distant parts 

 of the world, there is one to which some interesting contributions 

 have been made by the work of the Geological Survey of India, 

 and by the geologists of Australia and South Africa, and that a 

 short time might be profitably devoted to a consideration of a few 

 remarkable exceptions to the rule that similarity of faunas and 

 floras in fossil iferous formations throughout the surface of the 

 world implies identity of geological age. 



It has probably occurred to other geologists here present, as it 

 has to myself, to be engaged in examining a country the geology 

 of which was absolutely unknown, and to feel the satisfaction 

 that attends the first discovery of a characteristic fossil form. A 

 clue is at once afforded to the geology of the region ; one horizon 

 at least is believed to be determined, and from this horizon it is 

 possible to work upwards and downwards until others are found. 



It is, therefore, of especial importance to those engaged in 

 geological exploration to satisfy themselves whether the conclu- 

 sion is correct that identity, or close specific similarity, amongst 

 fossil forms, is a proof that the beds containing them are of the 

 same geological age. It has been pointed out by some of the 

 most careful thinkers, and especially by Forbes and Huxley, that 

 a species requires time to spread from one area to another, that, 

 in numerous cases, a migratory specific form must flourish in the 

 region to which it has migrated, after it has died out in its original 

 birthplace ; and that the presence of the same species in two 

 deposits at distant localities may rather tend to indicate that both 

 were not formed simultaneously. Huxley, as is well known. 

 invented the term "homotaxis" to express the relations between 

 such beds, and to avoid the possibly misleading expressions 

 "geological synchronism," and "contemporaneous origin." 



Despite such cautions, however, it still appears to be generally 

 assumed by palaeontologists that similarity between faunas and 

 floras is evidence of their belonging to the same geological 

 period ; that the geological age of any formation, whether 

 marine, fresh-water, or subaerial, can be determined by a com- 

 parison of its organic remains with those of other deposits, no 

 matter how distant, of which the position in the geological 

 sequence is ascertained : in short, that homotaxis of marine, 

 fresh-water, and terrestrial forms implies geological synchronism. 



That, as a general rule, homotaxis affords evidence that beds 

 exhibiting it belong approximately to the same geological period 

 appears supported by a large amount of evidence. But there 

 are some startling exceptions. I propose to notice a few typical 

 instances, several of them Indian, in which the system of deter- 

 mining the age of various formations by the fauna or flora has 

 led to contradictory results, before attempting to show wherein 

 the source of the error appears to lie. Nothing would be gained 

 and much time would be lost by entering upon the details of all 

 the cases known, even if I were able to give authentic particulars, 

 which is doubtful. It will be sufficient to cite some characteristic 

 examples, concerning the details of which satisfactory evidence- 

 is forthcoming. 



Pik-.rmi Beds. — There are but few fossiliferous deposits on the 

 face of the earth that have attracted more attention than the 

 Pikermi beds of Greece. In one of the most classical and 

 famous sites of the world, a few miles east of Athens, just 

 where 



The mountains look on Marathon, 

 A:iel Marathon looks on the sea, 



some red. silty beds occur, abounding in vertebrate remains. 



Some of the bones were described by Wagner and others, but 

 for a complete account of the fauna we are indebted to Prof. 

 Albert Gaudry, who has himself collected by far the greater 

 portion of the remains hitherto procured. The following is a 

 list of the genera determined ; it is unnecessary to give the 

 specific names : — 



MAMMALIA. 

 Primates. — Mesopithecus, i sp. 



Carnivora. — Simocyon, I ; Mustela, i ; Promephitis, I ; 

 Ictitherium, 3 ; Hycena, I ; Lepthy,ena, I ; Hyanictis, I ; 

 Felis, 4 ; Macharodus, 1 . 

 Proboscidea. — Mastodon, 2 ; Dinotherium, I. 

 Ungulata. — Chalicotherhtm, I ; Rhinoceros, 3 ; Acerotherium, 



1 ; Leptodon, I ; Hipparion, 1 ; S'us, 1 ; Catnelopardalis, 1 ; 

 Helladoiherium, 1 ; Orasius, 1 ; Pal&otragus, 1 ; Palceoryx, 



2 ; Tragocerus, 2 ; Palceoreas, 1 ; Antidorcas (?), 1 ; Gazella, 

 I ; Antitope, 3 ; Dnmotherium, 2. 



Rodentia. — Hystrix, 1. 

 Edentata. — Ancylotlierium, 1 . 



AVES. 

 Phasianus, 1 ; Gallus, 1 ; Gen. gallinac. indel., 1 ; Grus, 1 ; 

 Gen. dconidar, indet., 1. 



REPTII.IA. 

 Test 11 Jo, 1 ; Varanus, 1. 



Of Mammalia alone there are known from this deposit 31 

 genera, of which 22 are extinct, and 35 species. 



Now, this fauna is almost invariably in European works quoted 

 .1- Miocene. Of the species found no less than 14 — Simocyon 

 diaphorus, Ictitherium robuslum, /. hipparioaum, Hytzna eximia, 

 Hycenictis grceca, Machcerodus cultridens, Mastodon turicensis, 

 Dinotherium giganteum, Rhinoceros schleiermacheri, Hipparion 

 gracile, Sus crymanthius, Helta dotherium iuvernoyi, Tragocerus 

 amaltheus, and Gazella bievicornis — are met with in other 

 European deposits assigned to the Miocene period. It is true 

 that one of these deposits at least — that of Eppelsheim — has 

 been shown on stratigraphical grounds to be much more probably 

 Pliocene than Miocene, and the position of other deposits has 

 been determined by the kind of argument which, as I shall show, 

 has proved misleading in the case of Pikermi itself. Nevertheless 

 so general is the consensus of opinion amongst palaeontologists, 

 that the beds with Hipparion at Piker ni and elsewhere are 

 quoted as especially included in the Miocene system by the 

 French Committee of the International Geological Congress. 

 Amongst English writers the Miocene age of the Pikermi beds 

 appears generally admitted, as by Mr. Wallace (Geographical 

 Distribution of Animals, i. p. 115). Prof. Boyd Dawkins 

 ((>. /. G. S. 1880, p. 3S9), Mr. E. T. Newton (Q J. G. S. 1884, 

 pp. 284, 287, &c), and many others. Prof. Gaudry himself 

 is much more cautious ; he classes the fauna as intermediate 

 between Pliocene and Miocene, and only relegates it to Upper 

 Miocene because that is the position assigned by other palaeonto- 

 logists to beds containing remains of Hipparion. However, in 

 his subsequent works Prof. Gaudry has classed the Pikermi fauna 

 as Miocene. 



Now, the lowest of the beds with the vertebrate fauna at 

 Pikermi were by Prof. Gaudry himself found to be inter- 

 stratified with a band of gray conglomerate containing four 

 characteristic marine Pliocene Mollusca — Pee/en benedictus, Lam.; 

 Spondylus gatderoptts, L. ; Ostrea lamellosa, Brocchi ; and O. 

 mi, lata. Lam. It should be remembered that the Pliocene fauna 

 of the Mediterranean area is the richest and most typical in 

 Europe, and is as well known as any geological fauna in the 

 world. It should also be remembered thai, the Pliocene beds 

 are well developed in Greece at other localities besides Pikermi. 

 Prof. Gaudry especially points out that the vertebrate re- 

 mains, supposed to be those of Miocene animals, are deposited 

 in a stratum overlying a marine lied of undoubted Pliocene age, 

 and he proposes the following hypothesis to account for the pre- 

 sence of Miocene fossils in a Pliocene stratum. The remains 

 found at Pikermi are, he thinks, those of animals that inhabited 

 the extensive plains which in Miocene times extended over a 

 considerable proportion of the area now occupied by the Eastern 

 Mediterranean, and which united ( Ireece to Asia ; the plains were 

 broken up by the dislocations that took place at the close of the 

 Miocene period, and the animals escaped to the mountains, where 

 they died for want ■ if space and of food. Their bones were sub- 

 sequently washed down by the streams from the hills and buried 

 in the Pliocene deposits of Pikermi, 



