The greater part of the skin strongly ossified. On the back and sides the union of numerous quadrate or polygonal scutes forms a hard shield, usually consisting of an anterior (scapular) and posterior (pelvic) solid portion (which overhang on each side the parts of the body they respectively cover, forming chambers into which the limbs are withdrawn), and a variable number of rings between, connected by soft flexible skin so as to allow of curvature of the body. The top of the head has also a similar shield (cephalic), and the tail is usually encased in bony rings or plates. The outer or exposed surfaces of the limbs are protected by irregular bony scutes, not united at their margins; but the skin of the inner surface of the limbs and under side of the body is soft, and more or less clothed with hair. Hairs also in many species project through apertures between the bony scutes of the back. The ossified dermal scutes are everywhere covered by a layer of horny epidermis. Teeth numerous, simple, of persistent growth, and usually monophyodont, but in one genus (_Tatusia_) a succession of teeth has been observed. Zygomatic arch of skull complete. Cervical vertebræ with extremely short, broad, and depressed bodies. The atlas free, but the second and third, and often several of the others, ankylosed together both by their bodies and arches. Lumbar vertebræ with accessory zygomatic processes, and very large metapophyses, supporting the bony carapace. Clavicles well developed. A third trochanter on the femur. Tibia and fibula ankylosed at their distal extremities. Fore feet with strongly developed, curved claws, adapted for digging and scratching—three, four, or five in number. Hind feet plantigrade, with five toes, all provided with nails. Tongue long, pointed, and extensile, though to a less degree than in the Anteaters. Submaxillary glands largely developed. Stomach simple. Uterus simple. Placenta discoidal, deciduate. The brain is generally characterised by the large size of the olfactory lobes (Fig. 57), and the slight development of sulci on the hemispheres; the sylvian fissure being represented only by a very open and shallow angle. From the earliest stage of development the stapes is stirrup-shaped, thus showing a nearer affinity to the higher mammals than is presented by the Sloths.