Chap. XL] ANCIENT AND LIVING FORMS. 121 



the Vertebrata, until beds rich in fossils are discovered 

 far beneath the lowest Cambrian strata — a discovery of 

 which the chance is small. 



On the Succession of the same Types within the same 

 Areas, during the later Tertiary periods. 



Mr. Clift many years ago showed that the fossil 

 mammals from the Australian caves were closely allied 

 to the living marsupials of that continent. In South 

 America, a similar relationship is manifest, even to an 

 uneducated eye, in the gigantic pieces of armour, like 

 those of the armadillo, found in several parts of La 

 Plata ; and Professor Owen has shown in the most 

 striking manner that most of the fossil mammals, buried 

 there in such numbers, are related to South American 

 types. This relationship is even more clearly seen in 

 the wonderful collection of fossil bones made by MM. 

 Lund and Clausen in the caves of Brazil. I was so 

 much impressed with these facts; that I strongly insisted, 

 in 1839 and 1845, on this "law of the succession of 

 types/' — on "this wonderful relationship in the same 

 continent between the dead and the living." Professor 

 Owen has subsequently extended the same generalisation 

 to the mammals of the Old World. We see the same 

 law in this author's restorations of the extinct and 

 gigantic birds of New Zealand. 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 molluscs, 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. 



