SOME EXTINCT ARGENTINE MAMMALS 97 
Side by side with this well-defended creature there lived, 
however, another not less remarkable mammal, of nearly 
similar dimensions, and likewise belonging to the great 
order of edentates, then, as now, so characteristic of 
South America. This creature had, however, no such 
coat of mail as that which defended its contemporary 
(though there is a possibility that some bony granules 
may have been embedded in its skin), and as it appears 
to have been equally devoid of weapons of offence, while 
it did not derive protection from an arboreal life, it may 
be a matter of wonder how it managed to fight its way 
through the struggle for existence. That it did so is, 
however, perfectly clear, since the pigmy ground-sloth, as the 
animal in question may be called, is clearly the ancestral 
type from which were subsequently evolved those gigantic 
edentates of the Pleistocene deposits of the Argentine 
scientifically known by the names of Megalotherium, Mylodon, 
etc., but which may be collectively designated ground-sloths. 
These, although in some cases unprotected by any means 
of defence, were among the most gigantic of mammals, and 
they had, it is needless to say, no difficulty in holding their 
own; and it is only with regard to their pigmy ancestors 
that we have any cause for wondering how they managed 
to survive. Possibly these pigmy ground-sloths were 
burrowing creatures, like the great ant-eater of the present 
day, and lived in holes excavated by their powerful claws ; 
and if this should be the case, the difficulty as to their 
survival vanishes. 
Sloths are, however, such essentially arboreal creatures, 
as characteristic of the Brazilian forests as are squirrels 
and dormice of our own woods, that my readers will want 
to know what I mean by using such an apparently contra- 
dictory term as ground-sloths. 
