THE MAMMALIA. 51 



Miocene Tertiary of Europe and North America. But they 

 appear at once with their strange pecuHarities of dentition and 

 uncomfortable method of progression. In two genera of the 

 Edentata there are no teeth ; in the remaining members of the 

 order the teeth have no true enamel, are destitute of complete 

 roots, and the incisors are completely wanting in all but the arma- 

 dillos. The sloths and many other Edentates walk upon the 

 outside edges of their fore and hind limbs, with the claws of their 

 feet bent inwards. The sloths probably find this arrangement of 

 limb highly conducive to comfort, as they live hanging upside 

 down from branches of trees, and their claws form natural hooks. 

 The oldest representative of the Edentata, the gigantic Macrothe- 

 rhim of the Miocene Tertiary of France, walked in precisely . the 

 same way. The toes were furnished with immense claws, which 

 were bent inwards upon the palms of the hands and the soles of 

 the feet, owing to the bending of the first phalanges (finger and 

 toe-bones) upon the metacarpals and metatarsals. The most 

 celebrated of the great extinct " ground-sloths," Megatherium, 

 walked in the same way. It has been surmised that these great 

 sloths sat up on their haunches, supported by their powerful tails, 

 and grasped the trunks of trees with their powerful arms, either 

 wrenching them up by the roots or breaking them short off to the 

 ground, and then fed upon their leaves. Megatherium attained a 

 length of eighteen feet, and had bones more massive than those of 

 an elephant. The thigh-bone is nearly thrice the thickness of the 

 same bone in all existing elephants. Now, nothing can be 

 imagined more unwieldy or uncomfortable than for a peculiarly 

 huge and ponderous animal to walk on the outside edges of its 

 bent feet ! One must suppose it descended from some arboreal 

 form, of which the modern sloth is a surviving representative ; 

 that it was too stupid and heavy to accommodate itself to outward 

 circumstances, and so died out early in the struggle for life. 



The Edentata have wofully diminished, both in numbers of 

 species and in size. None survive in Europe, and but one genus 

 survives in Asia — the Manis, or scaly ant-eater. Two or three 

 species inhabit Africa, and the rest of the modern Edentata are to 

 be found in South Central America, where in Pliocene and Post- 

 Pliocene times they attained their greatest development. South 



