SOME EXTINCT ARGENTINE MAMMALS 99 



the two-toed sloth they are reduced to two ; in fact, the 

 feet are reduced to the condition of Httle more than hooks, 

 admirably adapted for suspending the animal back-down- 

 wards from the boughs of trees, but forming poor instruments 

 for terrestrial progression. Indeed, when on the ground 

 sloths walk slowly and awkwardly, with the soles of the 

 feet turned inwards, and the weight of the body supported 

 on their outward edges. It is important to notice that 

 in the skeleton of the feet the terminal bones, or those 

 ensheathed in the long claws, are not longitudinally grooved 

 on the upper surface. 



The South American, or true ant-eaters, one of which is 

 terrestrial while the other two are more or less arboreal 

 in their habits, are so unlike the sloths that it is difficult 

 to believe they have any near relationship with the 

 latter ; and, indeed, were it not for the extinct creatures 

 now under discussion, it would have been very difficult 

 to discover how close the connection between these two 

 groups really is. In place of the short and rounded 

 heads of the sloths, the ant-eaters have the head greatly 

 elongated and very slender, while the thin jaws are totally 

 devoid of teeth, and the tongue is long, cylindrical, and 

 highly extensile. There is, however, some degree of 

 variation in regard to the elongation of the skull, the 

 maximum development occurring in that of the great 

 ant-eater. If possible, a still greater difference obtains in 

 the structure of the feet, the fore-foot of the great ant-eater 

 having five toes, of which the middle one is vastly more 

 powerful than either of the others, while all but the fifth 

 have strong claws. In walking, the extreme outer side 

 and part of the upper surface of the fore-foot are applied 

 to the ground ; but in the hind-foot, which has the fourth 

 toe the largest and all the five digits furnished with claws, 



