CONCLUSIONS TO BE DRAWN FROM FOSSILS. 8 1 



are often more nearly related to types now living in the tropics than 

 to any others. As regards certain types — such as the ancient and 

 persistent genus Nautilus — some weight may be reasonably attached 

 to this argument. Another argument for the assumed uniformity of 

 climate in Palaeozoic time may be based upon the extraordinarily 

 wide range in space of many Palaeozoic types of animals. Upon 

 the whole, however, the Palaeozoic animals differ so widely from 

 their nearest living relatives as to render it very hazardous to base 

 on their supposed habits of life any decided conclusions as to Palae- 

 ozoic climate. Much the same may be said with regard to the 

 argument in favour of a very uniform and widely spread warm- 

 temperate climate during Carboniferous times, based upon the ex- 

 tension of the predominant Coal-plants to high northern latitudes. 



Taken collectively, our knowledge would rather go to show that 

 considerable variations in climate have occurred in all periods sub- 

 sequent to the appearance of living beings upon the earth. Thus, 

 there is more or less weighty evidence in favour of the occurrence 

 of Glacial periods in various of the older formations, beginning as 

 early as the Cambrian period. In Mesozoic time, certainly, the 

 evidence adduced by Neumayr, Marcou, and Trautschold seems to 

 show conclusively that different regions of the earth enjoyed, as 

 they do at present, different climates. The first of these observers, 

 in particular, has shown that a study of the animal life of the Jurassic 

 deposits of the north hemisphere would support the conclusion that 

 there existed during the Jurassic period three well-marked climatic 

 zones — one boreal, one temperate, and one subtropical — and that 

 two of these, at any rate, can be recognised in the south hemi- 

 sphere also. 



VOL. I. 



