io6 MOSTLY MAMMALS 



larger toes are marked by a longitudinal groove repre- 

 senting the cleft of those of the latter; and as in both 

 groups the middle toe is the largest, there is no reason 

 why the ant-eaters should not trace their origin to these 

 same pigmy ground-sloths or a closely allied type. In 

 this case the specialisation has resulted in a lengthening 

 of the skull and the loss of the teeth, the hind-foot having 

 retained more or less of the primitive type. Here like- 

 wise we must notice that the resemblance presented by 

 the skull of the scelidotheres to that of the ant-eaters 

 must be regarded as an instance of parallel development. 



From the structure of their teeth, the ground-sloths 

 were evidently pure vegetarians ; and the same may be said 

 of the sloths, which are animals specially modified for the 

 exigencies of an arboreal existence. On the other hand, 

 the ant-eaters, as their name implies, have given up a 

 vegetable diet and taken to living on ants, and to this may 

 be attributed their total loss of teeth. Should germs of 

 teeth ever be found in their jaws during an early stage of 

 existence, I venture to predict they will approximate in 

 structure to the teeth of the ground-sloths. 



I cannot conclude without saying a few words as to the 

 probable mode of life and external appearance of ground- 

 sloths. The Patagonian specimens have shown that, like 

 sloths and ant-eaters, they were clothed with a thick 

 covering of coarse hair. Further, from their massive 

 proportions, and also from their kinship to the sloths, 

 it is most likely that ground-sloths were as slow and 

 deliberate in their movements as the latter. That such 

 monstrous creatures could not have existed in a treeless 

 country like the Argentine Pampas has been already pointed 

 out, and we may hence assume that in the days of the 

 ground-sloths Argentina was much like what Brazil is at 



