MAMMALIA, 



feeding. The original bones and teeth of Megatherium, other 

 remains of Mylodon, and numerous parts of the skeleton of 

 Scclidotliei'ium (Fig. 68) are arranged in Wall-case 26. The 

 bones bear conspicuous crests and ridges, which indicate the 

 muscular power of these animals. The feet are twisted, 

 so that their side rather than their palm would be used when 

 walking ; and one, two, or three of the toes on each foot 

 terminate in a great claw. The fore quarters are arranged 

 for the easy motion of the grasping arms. The front of the 

 mandible is spout-shaped (see Figs. 68, 69), evidently adapted 

 to a long protrusible tongue, which could be used like that 

 of a giraffe for pulling leaves off the trees. The few grinding 

 teeth would continually grow as they were worn down 

 throughout life, and those of Megatherium (Fig. 69) are made 



Stand X. 

 Case Y. 



Stand X. 



Fig. G'J. — Lower jaw of Megatherium americanum, showing double- 

 ridged molar teeth and long spout-shaped symphysis (fZ), from the 

 Pampa Formation of Buenos Aires, Argentine Republic ; one-eighth 

 nat. size. (Wall-case 26.) 



extremely powerful l)y consisting of alternate soft and hard 

 plates of t()oth-sul)stance, which produce cross-ridges on the 

 crown. 



Tlie skeletons of the ground-sloths are wonderfully well 

 preserved in the Pampa Formation of the Argentine 

 Kepu])lic, and it is the rule rather than the exception to find 

 them whole. Most of them are discovered on the l)orders 

 of old lakes and rivers, evidently in the position in \\hich 

 the animals suddenly died. They are supposed to have 

 perished in the mud and soft ground when attempting to 

 reach the water to drink during dry seasons ; for drouglits 

 are common even at the present day in the country where 

 they formerly lived. In the time of tlie ground-sloths, 

 liowever, the pampa can scarcely have been the bare plain 

 that it is now ; it must have borne forest vegetation. 



Botli liuman Ijones and stone iiii])lements have occasionally 



Table-case 

 15a. 



