154 
FOSSIL MAMMALIA. 
toes.* The ulna (1) is extremely broad and a 
powerful at its upper extremity, affording large 9 
space for the origin of muscles, concerned in the 9 
movements of the foot. The radius (m) revolves a 
freely on the ulna, as in the Sloths and Ant- ■ 
eaters, both of which make much use of the 9 
fore leg, though for different purposes ; it has a I 
cavity at its upper end, which turns upon a 9 
spherical portion of the lower part of the hu- 9 
merus, and a large apoj^hysis (n), projecting from 9 
its longitudinal crest, indicates great power in 9 
the muscles that gave rotatory motion. 9 
The entire fore-foot must have been about a '9 
yard in length, and more than twelve inches | 
wide ; forming a most efficient instrument for j 
moving the earth, from that depth within which j 
succulent roots are usually most abundant. This 
great length of the fore-foot, when resting upon ] 
the ground, though unfavourable to progressive 
motion, must have enabled one fore-leg, when ^ 
acting in conjunction with the two hind legs and 
tail, to support the entire weight of the body ? ■ 
leaving the other fore-leg at liberty to be em' 9 
ployed exclusively in the operation of digging 9 
food.i J 
* There is a similar expansion of the lower part of the 9 
Humerus in the Ant-eater, which employs its fore feet in diggii'S ■ 
up the solid hills of the Termite Ants. 1 
+ At PI. 5, beneath Fig. 1, are represented the fore-foot of a” * 
Armadillo (Dasypus Peba), and the fore-foot of the Chlamy' 
phorus, each adapted, like that of the Megatherium, to form a'J 
