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THE GEOLOGICAL EVIDENCES OF EVOLUTION 
393 
the tree-kangaroos of New Guinea; a large wombat as large 
as a tapir ■ the Diprotodon, a thick-limbed kangaroo the size of 
a rhinoceros or small elephant ; and a cpiite different animal, 
the Nototherium, nearly as large. The carnivorous Thyla- 
cinus of Tasmania is also found fossil; and a huge phalanger, 
Thylacoleo, the size of a lion, believed by Professor Owen 
and by Professor Oscar Schmidt to have been equally carni¬ 
vorous and destructive. 1 Besides these, there are many other 
species more resembling the living forms both in size and 
structure, of which they may be, in some cases, the direct 
ancestors. Two species of extinct Echidna, belonging to the 
very low Monotremata, have also been found in New South 
"Wales. 
Next to Australia, South America possesses the most re¬ 
markable assemblage of peculiar mammals, in its numerous 
Edentata—the sloths, ant-eaters, and armadillos; its rodents, 
such as the cavies and chinchillas ; its marsupial opossums, and 
its quadrumana of the family Cebidse. Remains of extinct 
species of all these have been found in the caves of Brazil, of 
Post-Pliocene age ; while in the earlier Pliocene deposits of the 
pampas many distinct genera of these groups have been found, 
some of gigantic size and extraordinary form. There are 
armadillos of many types, some being as large as elephants ; 
gigantic sloths of the genera Megatherium, Megalonyx, Mylodon, 
Lestodon, and many others ; rodents belonging to the American 
families Cavidte and Chinchillidse; and ungulates allied to the 
llama; besides many other extinct forms of intermediate types 
or of uncertain affinities. 2 The extinct Moas of New Zealand 
—huge wingless birds allied to the living Apteryx—illustrate 
the same general law. 
The examples now quoted, besides illustrating and enforcing 
the general fact of evolution, throw some light on the usual 
character of the modification and progression of animal forms. 
In the cases where the geological record is tolerably complete, 
we find a continuous development of some kind—either in 
complexity of ornamentation, as in the fossil Paludinas of the 
Hungarian lake-basins; in size and in the specialisation of the 
1 See The Mammalia in their Relation to Primeval Times, p. 102. 
2 For a brief enumeration and description of these fossils, see the author’s 
Geographical Distribution of A nimals, vol. i. p. 146. 
