In the face the intermaxillary bone is well developed, and there is often a crest of bone passing over the top of the skull from side to side over the occiput, which is in relation to the head armour. The brain is small; the back or little brain is not covered by the brain proper, whose convolutions and processes are few and simple. The olfactory lobes project. [Illustration: GREAT ARMADILLO.] These armoured, round-bodied, short-legged, great-clawed animals are numerous, and there are several species, which need not, however, be collected into more than two genera. But it is by no means easy to arrange those of the first genus--the True Armadillos, genus _Dasypus_--in any other than an arbitrary and very artificial classification. Usually they are grouped and separated by the relative number of digits or claws on the fore and hinder extremities; by the presence or absence of teeth in the intermaxillary bones; by their ability to roll up; and by the excessive or the small number of their teeth. The method of walking, whether on the sole or on the tips of the claws, and the number of the bands, have been partly employed in classification, but their number is often variable in individuals of the same species. [Illustration: BRAIN OF THE ARMADILLO.] The Priodontes have but one species, which is readily distinguished by its superior size, besides by its great number of teeth, of which there are from twenty-two to twenty-four small ones on each jaw on each side, making from eighty-eight to ninety-six in all. THE GREAT ARMADILLO.[73] This is an inhabitant of Brazil, and of the northern parts of Paraguay and of Surinam, and is a dweller in the forest, being never found far out on the plains. The head is seven inches and a half long, and the ears, usually pointed and laid backwards, are not quite two inches in length. The head and body, without the tail, measure three feet and some inches, whilst the thickly-rooted but rapidlytapering tail is about a foot and a half in length. Hence the head is small for the body in this Armadillo, and the forehead is protuberant, and the face is very tubular and cylindrical-looking. The shoulder and croup shields are not expanded and solid, but consist of nine and eighteen rows of plates respectively, and the intermediate part of the body has twelve or thirteen movable bands, each of which is made up of rectangular scales, or scutes, about half an inch square. The circumference of the root of the tail is upwards of ten inches, and the organ is covered with plates, disposed in rings at the root, and not farther down, but forming spiral or crescent-shaped lines throughout the rest of its length.