710 



iiKroKT — 1884. 



M 





nnd so uniform is lliis lliroiij:liout lliat no si'])iirato rcj^'ions can In- fstalili.sliod, ^i 

 (liiit tlu'vo is but out! oceanic to cdntrnst with 1-1 tcvrcstriiil rcjiions. 



It is impossihlo to enter I'uitlier into tliia .sul))ect now, and I can only alliwlt' ; , 

 the (nidenci! in favour <if the existence of land-re;:ioiis in past times. It is Mur.t.y 

 necessary to romind you of tlie jjroofs alreatly accumulated of dillerences liolwffu 

 tlio faiiiui of distant countries in Tertiary times. The Koceiie, Miocene, and 

 Pliocene vertohrata of Nortli Americiv ditler quite as much from tho.^e of Kur .p. 

 in the saint! periods as ilo the ixenera of llio ])re>ent day; and tliere was as n;;; 'i 

 distinction hetweon tlie nianinialia of iht) Hinndnyas ami of (Ireece wli'eu ' 

 Siwalik and I'ilu'rmi faunas were living as there is now. In .Mesozoic tiuu -i v.. 

 have similar evidence. The reptiles of the American .lurassic deposits pnisf.t 

 wide differences from those of the J-airopean beds of that aj^e, and the yoiit!i 

 African re])tilian types of tlie Karoo beds are barely represented elsewhere. ];.• 

 there is no reason for siipposin;.' tliat tlie limits or relations of tlu' zooloi,'ical ui;! 

 botanical regions in ])ast times were the same as they now are. It is qnito ci'r':i. i 

 indeed that the distribution of land-areas, whether thi' jrreai oceanic tract has i.- 

 mained unchange<l in its jifonpral outlines or not, has underfrone enormous vnriatin, .^ 

 and the migration of the terrestrial fauna and llora must have been dependr. • 

 upon the presence or absence of land communiciitiou between dilU'rent coniinrii!.;! 

 tracts; in other W(mls, the terres-trial regiouHof jiast epoclis, alihoui.']ijnst ascit':i.:;. 

 marked as those of the present day, were very dill'erently distributed. Tiif !•- 

 morkable resemblance of the Uoras in the Karoo beds of Soutii Africa, tlio Dmii O 

 of India, and the coal-measures of Australia, and the wide dill'ereiice of ':.'.': 

 from any I'kiropean fossil llora, is a good example of the former distribution of liiV; 

 ■whilst it is. scarcely necessary to observe that tlu; present Neotropical and Austriili,.:; 

 mammals resemble those of the same countries in the later Tertiary times m i 

 more than they do the living mammalia of other regions, and that the Austrii'ia'i 

 mammal fauna is in all probability more nearly allied to the forms of life inliiu '.t- 

 ing Europonn the Mesnzoic era than to any Knrojiean types of later date. If :' >■ 

 existing mammals of Australia had all become extinct, a deposit containing iLcir 

 bonos would probably have been classed as Mesozoic. 



The belief in the former universality of faunas and floras is very ranch ! ii- 

 nected Avilh the idea onct; generally prevalent, nnd still far iVoni obsolete, that :'a^ 

 temperature of the earth's surface was formerly uniform, and that at all cvh!'.- 

 until early or even middle Tertiary times the poles were as warm as the equa' r, 

 and both enjoyed a constant tropical climate. The want of glacial evidence i. :ii 

 past times in Spitzbergen and Greenland, where a temperature capable of supp .rt- 

 ing arboreal vegetation has certainly prevailed dining several geological period'-, i? 

 counterbalanced by the gradually accumidating ])rools of Lower Mesozoic or I'liyer 

 Palaeozoic glacial epochs in South Africa, Australia, and, strangest of all, in India. 

 Even during those periods of the earth's history when there is reason to helievt 

 that the temperature in high latitudes was higher than it now is, evidence of distinct 

 zones of climate has been observed, and quite recently Dr. Neumayr,' of Vienn:i, 

 has shown that the distribution of Cretaceous and Jurassic evphalojwda thro..<.*h- 

 out the earth's surface proves that during those periods the warmer and ct^t'or 

 zones of the world existed in the same manner as at present, and that thty 

 affected the distribution of marine life as they do now. 



The idea that freah-water and torresl rial faunas and floraswere similar tlirou;;!iout 

 the world's surface in pa.st times is so ingrained in palseontological science tliat it 

 will require many years yet before the fallacy of the assumption is geneially 

 admitted. No circumstance has contributed more widely to the belief than the 

 supposed universal diffusion of the Carboniferous flora. The evidence that the 



Slants which prevailed in the coal-measures of Europe were replaced by totally 

 ifferent forms in Australia, despite the closest .similarity in the marine inhabitant? 

 of the two areas at the period, will probably go far to give the death-blow to an 

 hypothesis that rests upon no solid ground of observation. In a vast number 



' ' Ueber klimatischo Zoncn wilhrcnd der Juri;s- und Kreidczcit,' Dcnhtchr. Math. 

 jy«f. CI. Akatl. Wixt. men, vol. xlvii. 1883. 



^jiiyii^ 



