GENERAL CHARACTERS. 
203 
The foregoing are almost the only characters common to the whole of the 
Edentates. It may be added, however, that all these animals are of a comparatively 
low degree of organisation, although many of them are specialised for particular 
modes of life. In general their brains are relatively small, with the hemispheres, 
or anterior portion, devoid of convolutions, and not extending backwards to overlap 
and conceal the hinder portion or cerebellum. In some cases, however, the hemi¬ 
spheres of the brain are distinctly convoluted. Very frequently the shoulder-blade, 
or scapula, is characterised by the great development of the anterior portion of its 
lower extremity; this so-called coracoidal portion (of which we shall have to speak 
more fully when we come to the Egg-laying Mammals), being sometimes, as shown 
in our figure of the skeleton of the sloth, marked off from the remainder of the 
bone by a perforation, and suturally united with it. Certain members of the order, 
such as the armadillos and their extinct allies, are peculiar among Mammals in 
possessing a bony cuirass in the skin; while the pangolins are equally remarkable 
for the coat of overlapping horny scales with which the entire body is invested. 
From the absence of enamel in their teeth, and the presence of rudimental 
milk-teeth in some of their representatives, it is probable that the Edentates should 
be regarded as somewhat degenerate types, descended from ancestors provided 
with a double set of enamel-coated teeth. There are, however, no indications of 
any close relationship between the Edentates and any other of the Mammalian 
orders; and it is accordingly pretty evident that they are descended from extinct 
primitive Mammals quite independently of all other members of the class. 
As already mentioned, the sloths, ant-eaters, and armadillos, are 
entirely confined to the New World; and since it is these alone which 
form the typical Edentates, the order is essentially an American one. Indeed, 
there is a considerable degree of doubt whether the Old World pangolins and 
aard-varks, which form its only other representatives, are rightly included within 
the order; their organisation being very different from that of the typical forms. 
Be this as it may, the typical Edentates appear to have been always confined 
to the New World, in the southern half of which they attained their greatest 
development; for while fossil forms are abundant in America, they are unknown 
elsewhere. 1 Some of these extinct types are of the greatest importance to the 
zoologist, since they serve to connect together most intimately such widely different 
forms as the arboreal sloths and the terrestrial armadillos. 
Although varying greatly in their mode of life, the whole of the 
Mode of Life. £ c | en ^- a ^ es —both living and extinct—are either arboreal or terrestrial, 
none of them being modified either for flight in the air or for swimming in the 
water. While the purely arboreal sloths are entirely vegetable feeders, all the 
other members of the order, of which a few are likewise more or less arboreal in 
their habits, subsist on flesh or insects. Moreover, several of these carnivorous 
forms are burrowing animals; and it is remarkable that the members of three 
distinct groups, namely, the ant-eaters, the pangolins, and the aard-varks, subsist 
mainly, or exclusively, on white ants or termites; the only other purely ant-eating 
members of the class belonging respectively to the Pouched Mammals and the Egg- 
1 Certain remains from the Tertiary rocks of France have been considered to belong to armadillos, but this 
determination is exceedingly doubtful. 
