114 DARWINIAN A. 



faunas and floras, and in nearly the same proportions 

 and the same diversities as at present. The faunas of 

 what is now Europe, Asia, America, and Australia, 

 differed from each other much as they now differ : in 

 fact — according to Adolphe Brongniart, whose state- 

 ments we here condense ' — the inhabitants of these 

 different regions appear for the most part to have ac- 

 quired, before the close of the tertiary period, the 

 characters which essentially distinguish their existing 

 faunas. The Eastern Continent had then, as now, its 

 great pachyderms, elephants, rhinoceros, hippopota- 

 mus ; South America, its armadillos, sloths, and ant- 

 eaters ; Australia, a crowd of marsupials ; and the very 

 strange birds of New Zealand had predecessors of simi- 

 lar strangeness. Everywhere the same geographical 

 distribution as now, with a difference in the particular 

 area, as respects the northern portion of the continents, 

 answering to a warmer climate then than ours, such 

 as allowed species of hippopotamus, rhinoceros, and 

 elephant, to range even to the regions now inhabited 

 by the reindeer and the musk-ox, and with the seri- 

 ous disturbing intervention of the glacial period with- 

 in a comparatively recent time. Let it be noted also 

 that those tertiary species which have continued with 

 little change down to our days are the marine animals 

 of the lower grades, especially mollusca. Their low 

 organization, moderate sensibility, and the simple con- 

 ditions of an existence in a medium like the ocean, 

 not subject to great variation and incapable of sudden 

 change, may well account for their continuance; 

 while, on the other hand, the more intense, however 



1 In Comptes Rendus, Academie des Sciences, February 2, 1857. 



