18 
NOTICE OF THE MEGATHERIUM. 
the implanting of long-rooted teeth. Its dental formula was the same, but the teeth were of 
a structure slightly less simple than those of the Megatherium. The vertebral column of the 
Mylodon, moreover, presented notable peculiarities which distinguished it from its larger 
congener. The lumbar vertebrae were not free, but were anchylosed firmly to each other 
and to the sacrum, forming of the whole a long, massive arch, — a structure peculiar to Birds 
in the present creation. It is interesting to contemplate these Megatheroid animals in their 
relations to the leaf-eating quadrupeds of the present day. The elephant, the largest of 
existing phyllophagous animals, is characterized by a maximized proboscis, by which, as with 
a long dexterous arm, it wrenches off the lower branches of trees, and gathers their leaves to 
convey them to his almost tongueless mouth. The proboscis thus becomes, for this monarch 
of beasts, the organ upon which its whole existence depends, and which brings the rest of its 
structure in harmony with the necessities of its life. The Giraffe possesses another and entirely 
different mechanism for gaining the same final end. Elevated by means of fore-legs and a neck 
which are both of unparalleled longitudinal extension, the head is itself brought to the height 
of the boughs, from which it rapidly strips the leaves and tender twigs, by seizing them with 
its flexible lips and long muscular tongue. The Sloth, with its short, lighter body, leaves 
the ground entirely, and, climbing up along the higher and outer branches, uses its long arms 
and hooked claws in drawing the ends of the slender boughs so near to it that it can browse 
upon their leafy extremities. The structure of these three animals, although so diverse, admi- 
rably adapts them to a common food. But what modifications of the bodily frame could 
have permitted animals of approximate bulk to the Elephant and Giraffe, yet neither pro- 
boscidian nor of towering stature, to have fed like them upon the high-waving branches 
of trees, is a problem in comparative anatomy which the fossil bones of the Megatheroids 
have alone enabled us to solve. The great prototype of the modern Sloth could neither reach 
up to the branches which it coveted, nor attain to them by climbing in the tree itself; but 
its strong arms could seize the truck with a vice-like grasp, and, acting in unison with the 
muscles of its immense hinder extremities, could sway it back and forth, until it fell prostrate, 
bringing with it its large supply of choice nourishment. It would be difficult to conceive of 
any modifications of the Sloth’s structure whereby a creature of like needs, yet of dimensions so 
immense as to totally unfit it for an abode in trees, might still derive from them its sustenance, 
more simple and more effectual than those which the skeleton of the Megatherium has 
shown us. 
