246 THE DOCTRINE OF DESCENT. 
diluvial fauna of South America collected by Lund, 
Castlenau, and Weddell, from the Brazilian caves, and 
the alluvium of the Pampas, among the 118 species cited, 
actually includes, in addition to those already mentioned, 
as being of . probably Old-World pedigree, no less than 
35 species of Edentata, and these animals of consider- 
able bulk. Not reckoning the.36 rodents and bats, and 
the smaller fauna in general, they constitute nearly half 
of the larger diluvial animals of South America. The 
assemblage of Edentata previously settled in these 
regions thus held their own against the invasion from 
the north. 
It is comprehensible that the same external causes 
which led the march of the children of the north con- 
stantly further, may likewise have invited the members 
of the antarctic fauna to extend themselves northwards. 
As we even now encounter the incongruous forms of 
the sloth, the armadillo, and the ant-eater in Guatemala 
and Mexico, in the midst of a fauna in great part con- 
sisting of races still represented in Europe, we also find, 
even in diluvial eras, gigantic sloths and armadillos 
ranging far into the north. Megalonyx Jeffersoni, and 
Mylodon Harlemi, sentries of South American origin 
thrown out as far as Kentucky and Missouri, are a 
phenomenon as heterogeneous in the land of the bison 
and the deer, as is the mastodon in the Andes of New 
Granada and Bolivia. Over the whole enormous extent 
of both portions of the New Continent, the mixture 
and interpenetration of two mammalian groups of com- 
pletely diverse families, constitutes the most conspicuous 
feature of its fauna; and it is significant that each 
group increases in the abundance of its representatives 
