. Cassell's natural history. Animals; Animal behavior. 162 NATURAL BISTORT. Some small tail bones exist, for that organ is rudimentary in all the Sloths, there being a stump iri the Ai, and eleven very small bones ; but in the Two-fingered Sloths the tail is not visible, vnd there are four little ossicles. There are no long and very prominent spines to any of the back bones, and the whole bony column of the spine is readily curved and bent. The animals so constantly bring the liands and feet together, when hanging, that a ready bending of the spine is absolutely necessary. Moreover, in
. Cassell's natural history. Animals; Animal behavior. 162 NATURAL BISTORT. Some small tail bones exist, for that organ is rudimentary in all the Sloths, there being a stump iri the Ai, and eleven very small bones ; but in the Two-fingered Sloths the tail is not visible, vnd there are four little ossicles. There are no long and very prominent spines to any of the back bones, and the whole bony column of the spine is readily curved and bent. The animals so constantly bring the liands and feet together, when hanging, that a ready bending of the spine is absolutely necessary. Moreover, in sleeping they often rest in the fork of a tree, or on i between the hind legs, rolling the body up as it were in a ball, and th construction of the long chain of back bones with small spines. The most distinctive character of the skeleton of the Sloth is tl: limb over the hind one. An examination of the slender bones of the ; solid than those of most Mammals. The arm bone (humerus) has a expanded part, just above the elbow (inner condyle), in the Ai; but this branch, and place the head is facilitated by the peculiar excess of length of the fore •m shows that they are more hole through it in the inner not found in the two-toed. kinds. The wrist and hand are long and narrow, and this is produced by the union of some bones which are separate in other Mammalia, and the slight development of others. Thus there are six bones in the wrist instead of eight (the scaphoid and trapezium, and the OS magnum and trapezoid have coalesced). In the Ai there are tliiee clawed fingers, and the bones of the thumb and of the little hngei are absent, and their corresponding hand bones (metacarpals) aie ^ery small, and are joined on to the next, that is, to the metacarpal of the index and third finger. The three fingers are, moreover, strengthened for their peculiar uses, the first two joints being united, and the tip or last joint being \eiy long, and supiioi-ting the claw. Moreover, as the long c
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