GEOLOGICAL SUCCESSION OF ORGANIC BEINGS 129 



tn the caves of Brazil. I was so mucli impressed with 

 these facts that I strongly insisted, in 1839 and 1845, on 

 this "law of the succession of types" — on "this wonder- 

 ful relationship in the same continent between the dead 

 and the living." Professor Owen has subsequently ex- 

 tended the same generalization to the mammals of the 

 Old World. We see the same law in this author's res- 

 torations of the extinct and gigantic birds of New Zea- 

 land. We see it also in the birds of the caves of Brazil. 

 Mr. Woodward has shown that the same law holds good 

 with sea-shells, but, from the wide distribution of most 

 moUusks, it is not well displayed by them. Other cases 

 could be added, as the relation between the extinct 

 and living land-shells of Madeira; and between the 

 extinct and living brackish water-shells of the Aralo- 

 Caspian Sea. 



Now what does this remarkable law of the succession 

 of the same types within the same areas mean ? He 

 would be a bold man who, after comparing the present 

 climate of Australia and of parts of South America 

 under the same latitude, would attempt to account, on 

 the one hand, through dissimilar physical conditions, for 

 the dissimilarity of the inhabitants of these two conti- 

 nents; and, on the other hand, through similarity of 

 conditions, for the uniformity of the same types in each 

 continent during the later tertiary periods. Nor can it 

 be pretended that it is an immutable law that marsupials 

 should have been chiefly or solely produced in Australia; 

 or that Edentata and other American types should have 

 been solely produced in South America. For we know 

 that Europe in ancient times was peopled by numerous 

 marsupials; and I have shown in the publications above 



