GIANT SLOTHS AND ARMADILLOS. 183 
Mylodon. Though of smaller size, it was much bigger than any 
living sloth, and attained a length of eleven feet. It has the same 
general structure, but the head and jaws are somewhat different, 
and more like the recent forms. A nearly perfect and original 
skeleton of Mylodon gracilis has been set up beside its huge 
relative’s cast in the same gallery at the Natural History Museum. 
The crowns of its molar teeth are flat instead of being ridged ; 
hence its name, which signified “ mill-toothed.” 
Yet another was the Scelidotherium ^ with its long limbs. 
Darwin obtained an almost entire skeleton of one of these. It 
was as large as a polar bear. Speaking of his discovery, he says, 
“ The beds containing the fossil skeletons consist of stratified 
gravel and reddish mud ; a proof that the elevation of the land 
has been inconsiderable since the great quadrupeds wandered 
over the surrounding plains, and the external features of the 
country were then very nearly the same as now. The number of 
the remains of these quadrupeds embedded in the vast estuary 
deposits which form the Pampas and cover the granitic rocks of 
Banda Oriental must be extraordinarily great. I believe a 
straight line drawn in any direction through the country would 
cut through some skeleton or bones. As far as I am aware, not 
one of these animals perished, as was formerly supposed, in the 
marshes or muddy river-beds of the present land, but their bones 
have been exposed by the streams intersecting the subaqueous 
deposit in which they were originally embedded. We may con- 
clude that the whole area of the Pampas is one wide sepulchre of 
these extinct gigantic quadrupeds.” ^ 
The genus Scelidotherium comprises a number of species and 
presents characters more or less, intermediate between Mega- 
therium and some other genera. The skull is low and elongated, 
and shows an approach to that of the modern ant-eater. The 
feet also are different from those of Megatherium (see Fig. 50). 
These monster sloths inhabited South America during the 
^ Greek — scelis^ limb; therion^ beast. ^ Journal of Researches. 
