CflAP. X. 
SxiME TYPES m SAME AKEAS. 
339 
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 mar¬ 
supials 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 arma¬ 
dillo, 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 relation¬ 
ship is even more clearly seen in the wonderful collec¬ 
tion 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 won¬ 
derful 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 distribu¬ 
tion of most genera of 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. 
Now what does this remarkable law of the succes¬ 
sion of the same types within the same areas mean? 
He would be a bold man, who after comparing the pre¬ 
sent climate of Australia and of parts of South America 
under the same latitude, would attempt to account, on 
the one hand, by dissimilar physical conditions for the 
dissimilarity of the inhabitants of these two continents, 
Q 2 
