The shell of this Armadillo is blackish-brown, and the skin between the central bands is bald and smooth. There are nine back teeth on each side in both jaws, and there are none in front. The muscles which enable this Armadillo to bring its tail and nose together and to form a ball shape, are not simply expansions of the common muscular tissue, which exists deeply in the skin in so many animals, but are special structures. The most important are in relation to the position of the head, neck, limbs, tail, and the shields and bands, when the body is about to be and while it is being rolled up; and these roller-up muscles are so arranged as to permit of the large liver and other internal organs not suffering pressure during their natural or temporary displacement. On the other hand, the unrollers act when the body and bones are in the rolled-up condition. The muscles of the back are very tendinous, and to a degree they unroll the animal, but this is also performed by muscles which are attached underneath the first movable band of armour, and to the front part of the spine of the blade bone; this will tend, when it contracts, to pull out the legs and protrude the fore part of the body, the centre being still rigid. Another drawer-back of the bladebone assists in this action, and it is inserted into the front or chest shield. The rolling up is done by the action of muscles which draw the nose down, so as to make the long head at right angles to the neck; then the fore-legs and bladebones are drawn in and up. At the same time, the muscles which pull down the tail act on the hind shield, and draw it down and forwards. The legs are pulled up, and then a great muscle, which is largely attached to the front and hind shields, and has a tendon-like expansion in the middle of its course beneath the movable bands, contracts and pulls front and stern together. The muscles of the loins, which in jumping animals bring the spine to a curve, do not act, and indeed are excessively small. The chief bend in the back is between the second and third lumbar vertebræ. (Murie.) GENUS CHLAMYDOPHORUS.--THE PICHICIAGO.[80] [Illustration: PICHICIAGO.]