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." 2 



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 

 1 Gree scelis, limb; therion, beast. * Journal of Researches. 



