110 MYLODON limbs short and massive, with feet as long as the thigh bones, set at right angles to the leg, and with the sole turned slightly inward ; the tail as long as the hind limbs, very thick, and affording a firm support in the semi-erect po- sition ; the chest long and large, protected by Mylodon robustus (restored). 16 pairs of ribs, broad and strongly attached to a well developed sternum; the scapulae unusually broad ; arm bones thick and short, with strong processes for muscles ; the bones of the forearm longer than those of the leg ; the skull smaller than that of the ox, but long, narrow, with a truncated muzzle, and support- ed by a short neck of seven vertebrae ; dorsal vertebrae 16, with broad and high spinous pro- cesses nearly equal and having a uniform back- ward inclination. Such proportions are found in no living animals, and only in the megathe- rioids among fossils. The skull presented two extensive fractures, from which the animal had recovered ; the air cells extend from the fron- tal and ethmoidal sinuses into the cranial bones, separating the two tables of the skull some- times for the extent of 2 in., forming a great protection against injury from falling limbs of trees. They were probably peaceful ani- mals like the existing sloths, though able to inflict severe wounds by their sharp and heavy claws ; the muscular strength of the edentates is very great, and must have been immense in all the megatherioids. While presenting the closest affinity to the small arboreal sloths, the mylo- don, with its claw-armed inner toes, had the outer thick and stunted, and evidently envel- oped in a kind of hoof, giving the power of standing and walking firmly as well as digging and seizing in this respect marking a tran- sition between edentates and pachyderms. It is now generally admitted that this animal com- menced the process of .prostrating trees by scratching away the soil from their roots, and loosening them from their attachments ; then, seizing the branches or trunk, and supported on the hind limbs and tail, it swayed the tree MYKMECOBIUS to and fro, and soon brought it to the ground
- o be stripped at its leisure ; in case of meeting
a tree too large to be uprooted, it is probable
- hat some of the smaller species, as indicated
3y the inward turning of the soles, possessed
- he faculty of climbing to the larger branches
within reach of the foliage. In regard to the means of stripping off leaves, Prof. Owen, from
- he cavity in the mastoid process for the articu-
.ation of the hyoid bone, and the large size of the anterior condyloid foramina whence issue the motor nerves, maintains that there was a remarkable development of the tongue ; this is also indicated by the broad, smooth, concave surface of the symphysis of the lower jaw, which, with the absence of incisors, offered no obstacle to its free motions, and provided space for it when retracted ; the megatherium had a short proboscis, prehensile lips, and a smaller tongue in a narrower mouth ; the elephant has a maximum proboscis, the giraffe a maximum tongue, the megatherium being intermediate; the mylodon, having no proboscis, had a largely developed tongue for stripping off foliage, con- trasting in this respect with the almost tongue- less elephant. While the megatherium may have measured 18 ft. from the fore part of the skull to the end of the tail, following the curve f the spine, the mylodon measured only 11 ft. ; other measurements in these animals respec- tively were : circumference at pelvis 14 and 9f ft. ; length of skull 2 and H ft., greatest width 1| and | ft. ; length of lower jaw 25 and 15^ in., width at symphysis 5f- and 5^ in. ; length of anterior limb 10 and 4% ft. ; clavicle 15 and 8| in., humerus 2 and l| ft., ulna 25 and 14% in., radius 26 and 11 in. ; fore foot 31J and 14 in. long, and 14 and 8 wide ; mid- dle and longest claw 10 and 5 in. ; width of pelvis 61 and 41 in. ; length of femur 28 and 19 in., circumference over great trochanter 3 and 2| ft., and width at same point 16 and 9 in. ; tibia 22 and 8|- in. ; length of hind foot 34^ and 19 in., width 12 and 6| ; heel bone IT and 7|- in. ; middle and largest claw 9 and 5 in. ; and width of largest vertebra of tail 21 and 10$- in. The scelidotherium (Gr. a/ce^tf, hind leg, and dqpiov, animal) is another extinct me- gatherioid, remarkable for the size of the hind limbs ; a nearly entire cranium shows the es- sential characters of the sloth's skull, with the mylodontal modifications of the complete zy- goma and shape of the lower jaw ; the teeth were f if , the upper triangular ; the form was massive. Pictet mentions seven species, vary- ing in size from a hog to an ox, which lived in South America during the diluvial epoch. Some other genera have been described by Owen, Pictet, and Leidy. MYRIAPOD. See CENTIPEDE. MYRMECOBIUS, a genus of marsupial animals, established by Waterhouse, of which the typ- ical species is the M. fascia tus of southern and western Australia. The teeth are very numerous, being incisors , canines |l|, pre- molars -|i|, molars |zf =52. The fore feet are
