178 EDENTATA 
limited area of distribution, and their small size compared with 
known ancestral forms, all show that this is an ancient and a waning 
group, the members of which seem still to hold their own either by 
the remoteness and seclusion of their dwelling-places, by their 
remarkable adaptation of structure to special conditions of life, or 
by aid of the peculiar defensive armature with which they are 
invested. Their former history can, however, only be thus surmised, 
rather than read, at present ; for, though we have ample evidence 
of the abundance and superior magnitude of certain forms in the 
most recent or Pleistocene geological age, yet we have at present 
no definite evidence as to their origin, or relationship to other 
orders of mammals. 
The existing members of the order readily group themselves 
into five distinct families, the limits of which are perfectly clear. 
These are (1) Bradypodide, or Sloths; (2) Myrmecophagide, or Ant-. 
eaters ; (3) Dasypodide, or Armadillos; (4) Manide, Pangolins or 
Scaly Anteaters; and (5) Orycteropodide, Aard-varks or African 
Anteaters. The geographical distribution of these families coincides 
with their structural distinction, the first three being inhabitants of 
the New and the last two of the Old World. It has been usual to 
arrange these families into two large groups or suborders: (1) the 
Phyllophaga, leaf-eaters, also called Tardigrada, containing the 
Bradypodide alone; and (2) the Entomophaga, insect-eaters, or 
Vermilingua, containing all the other families, from which some- 
times the Orycteropodide are separated as a third suborder under 
the name of Effodientia, or Tubulidentata. Such an arrangement 
is, however, an artificial one, founded on superficial resemblance. 
The bonds which unite the Munidw to the Myrmecophagide are 
mainly to be found in the structure of the mouth, especially the 
extensile character of the tongue, the great development of the sub- 
maxillary glands, and the absence of teeth. These characters are 
exactly analogous to those found in the Echidna among Monotremes, 
the Woodpeckers among Birds, and the Chameleon among Reptiles, 
—the fact probably being that in countries where Termites and 
similar insects flourish various distinct forms of vertebrates have 
become modified in special relation to this abundance of nutritious 
food, which could only be made available by a peculiar structure of 
the alimentary organs. A close study of the more essential 
portions of the anatomy of these animals! leads to the belief 
that all the American Edentates at present known, however di- 
versified in form and habits, belong to a common stock. Thus the 
Bradypodide, Megatheriide, and Myrmecophagide are certainly allied, 
the modifications seen in the existing families relating only to food 
and manner of life. The ancestral forms may have been omni- 
1 See Flower, ‘‘On the Mutual Affinities of the Animals composing the 
Order Edentata,” Proceedings of the Zoological Society, 1882, p. 358. 
