VIII MEGATHERIUM Kos 
negatived this supposition. It has shown that the Armadillos 
are in this matter the nearest relatives of Glossotheriwm. This 
result is important as tending further to confirm the close inter- 
relationship of all the American Edentates as contrasted with the 
Old-World forms—a matter which has already been emphasised. 
It is suggested, however, that the absence of under fur, which is 
so well developed in the Sloth, and the difference shown in trans- 
verse sections from the hair of Myrmecophaga, may be explained 
by difference in habitat. Glossotheriwm lived under conditions 
similar to those under which the Armadillos live to-day. Thus 
the outer covering of the body became alike in the two cases, the 
same needs supervening in both genera. 
Lestodon is another allied genus, which seems to possess 
canines. At any rate, in front of the four molars, and separated 
from them by a diastema, is a smallish, somewhat canine-lke 
tooth, in both jaws. 
Megalonyx and its allies are sometimes placed in a distinct 
family, Megalonychidae. JJegalonyx itself had a skull very 
like that of Bradypus, being shorter and not so elongated as 
in the Mylodontidae. There is a strong tusk anteriorly, which 
is separated by a considerable space from the three molars lying 
behind it. Both pairs of limbs seem to have possessed five toes. 
This is a North American genus. It differs from the bulk of 
the American Edentates in having a complete jugal arch. 
Megatherium is the type of yet a third family, Megatheriidae, 
of the Gravigrade Edentates. This creature is familiar from 
the many restorations which have been built up, and from its 
huge bulk, little short of that of an elephant. The skull, which 
is small for the size of the creature, has a complete jugal 
arch, from the middle of which depends a downward process as 
in other allied forms. The teeth grow to an extraordinary 
depth, and there are five of them in the upper and four in the 
lower jaw—on each side of course. The fore-limbs of the 
Megatherium are very much more slender than the enormously 
bulky hind-limbs, upon which and the equally massive tail the 
animal seems to have supported itself while tearing down 
branches of trees, upon whose leaves it fed. In the scapula 
the acromion joins the coracoid as in Bradypus; the clavicle is 
large. The fore-limb is four-toed, and the hind-limb three-toed. 
The latter has but one clawed digit (the third, i. the inner). 
