41 6 ORDERS OF MAMMALIA. 



lous, and the posterior tetradactylous, the two external digits 

 being nailless. 



Megalonyx, unlike the preceding, has been found in both 

 North and South America. It has the same number of teeth as 

 Megatherium and Mylodon, but the crowns of these are exca- 

 vated centrally and have a prominent margin. The fore-limbs 

 are shorter than the hind-limbs, and the calcaneum is unusually 

 long. Megalonyx was probably about the size of an ox. 



Just as the Sloths of the present day were formerly repre- 

 sented in the same geographical area by the gigantic Megathe- 

 roids, so the little banded and cuirassed Armadillos of South 

 America were formerly represented by gigantic species, con- 

 stituting the genus Glyptodon. The Glyptodons (fig. 345) 

 differed from the living Armadillos in having no bands in their 

 armour, so that they must have been unable to roll themselves 

 up. It is rare at the present day to meet with any Armadillo 

 over two or three feet in length ; but the length of the Glypto- 

 don davipes, from the tip of the snout to the end of the tail, 

 was more than nine feet. 



Fig. 345. Glyptodon davipes. Post Pliocene, South America. 



There are no canine or incisor teeth in the Glyptodon, but 

 there are eight molars on each side of each jaw, and the crowns 

 of these are fluted and almost trilobed. The head is covered 

 by a helmet of bony plates, and the trunk was defended by an 

 armour of almost hexagonal bony pieces united by sutures, and 

 exhibiting special patterns of sculpturing in each species. The 

 tail was also defended by a similar armour, and the vertebras 

 were mostly fused together so as to form a cylindrical bony 

 rod. The feet are massive, and the ungual phalanges short and 

 compressed. 



Besides the various species of Glyptodon, South America has 

 also yielded the remains of several true species of Dasypus, 

 nearly allied to the living Armadillos. These have been found 



