The diminutive fore limbs are separated by narrow shoulders, and although the upper arm is short and well furnished with muscles, the fore arm is long, slender, but very movable. The hand is short and broad, and there are four curved, sharp claws, the first one, or thumb, being the smallest, and the third and fourth the largest. The hair covers over the fingers to the claws, which can separate widely, grasp and hold, and be bent on the palm. The movements of the wrists and fore arms are considerable, and a large and long upward-turning muscle is in the space between the ulna and radius (the bones of the arm). Moreover, the ulna joints with a cavity in the cuneiform bone of the wrist; and the first row of wrist bones has three in it, and the second has four. The first phalanges, or those of the thumb, are not placed as a thumb in relation to the wrist bones, and it is the outer fingers that grasp with their claws. As the Kangaroo has to lift up its arm, there is a collar-bone, and the arm bone (humerus) is perforated on the inner side of the end above the elbow; and the olecranon is long. The bladebone has a curved ridge, and the muscles of the upper part are less than those which are attached to the part below it. There are thirteen pairs of ribs to the chest. The skull is long and comparatively smooth, and even the ridges for the temporal muscles are only slightly raised; and in old Kangaroos the bones do not unite or anchylose as they do in the other Mammalia hitherto noticed. The teeth are not used as weapons of offence, but simply to graze with, and the lower jaw is not quite solid at the chin, but only so below, so that the lower incisors can be slightly separated. The ear-bone is remarkable for being separated into three parts, namely, the temporal or squamous, the petrosal, and the tympanic; and this is rather a reptilian character. Moreover, the air-chambers of the side of the under part of the skull are in the form of rounded prominences, or “bullæ.” They are situated in the lower part of the ear-bone, called squamosal. The zygoma, or process between the cheek (malar) bone and the ear, is hollow, complete, and arched, its front part being, moreover, extended downwards in a projection which reaches below the grinding teeth, and resembles that of the Sloths somewhat. The lower jaw has its back part, or angle, bent inwards (or inflected) strongly, and this is, except in one set, a characteristic of the Marsupiata. [Illustration: STOMACH OF THE GREAT KANGAROO. ([_œ_]) œsophagus; (_in_) intestine.]