102 THE NEOG^IC REALM. [CHAP. 



highly specialised as regards the structure of their limbs, in the 

 present group the greatest degree of specialisation shows itself in 

 the skull, in the majority of the species. There are but three 



FlG. 22. TAMANDUA ANTEATER. 



members of the family, each representing a genus by itself, namely 

 the great anteater (Myrmecophaga\ the tamandua (Tamandua], and 

 the two-toed or little anteater ( Cycloturus] ; the latter being ex- 

 clusively arboreal in its habits. 



The foregoing remarks on some of the structural features of 



the sloths and anteaters will the more easily enable 

 si?th s Und " the rea der to understand the peculiarities of the 



extinct group of ground-sloths. They have been 

 divided into a large number of genera and several families; but 

 the former may be considerably reduced, and the whole of them 

 included in the single family Megalotheriidce. Ranging in the 

 Argentine from the Santa Crucian to the Pampean epoch and the 

 overlying sand-dunes, the family has a geographical distributional 

 area including North America as far as Kentucky. The South 

 American forms vastly exceed those of N. America in point of 

 number; and whereas the latter are found only in deposits of 

 upper Pliocene and Plistocene age, the former, as we have seen, 

 extend downwards to the Miocene. The members of this family 

 may be denned as edentates without a carapace, the skull and 

 dentition of the general type of those of the sloths, and the 



