622 LAND MAMMALS IN THE WESTERN HEMISPHERE 



panded, but faced outward, and its hinder end, curved upward 

 and thickened, was another point of strong support for the 

 carapace. The two elements together formed an inverted 

 arch, the crown of which rested on the head of the femur. 



Though less massive than those of the hind leg, the bones of 

 the fore limb were yet very heavy. The humerus was short 

 and had reduced deltoid and supinator ridges and no epicondy- 

 lar foramen ; the short fore-arm bones were separate and heavy, 

 the ulna especially so. The femur was much the longest of the 

 limb-bones and was extremely strong, especially in its great 

 breadth, the antero-posterior flattening, common to nearly all 

 very heavy mammals, being well marked. A very unusual 

 feature was the position of the third trochanter near the lower 

 end of the shaft. The tibia and fibula were much shorter than 

 the femur, extremely heavy and coossified at both ends. The 

 very short and broad feet retained five digits; in the manus 

 the claws were sometimes comparatively long and sharp, some- 

 times blunt and hoof-like ; those of the hind foot were always 

 broad hoofs. 



Among all the many strange and grotesque mammals 

 which the study of fossils has brought to light, none can have 

 been more remarkable than the Pleistocene fglyptodonts ; 

 slow-moving hillocks they must have seemed, the larger species 

 12 to 14 feet long and 5 feet or more in height. Those that had 

 claws on the fore feet probably used them to dig for roots and 

 tubers, but' all were plant-feeders. When attacked by the 

 fsabre-tooth tigers {^Smilodon) or the great bears {\Arcto- 

 therium) they needed only to squat down, bringing the edges 

 of the carapace to the ground, and draw in the head, to be 

 perfectly protected, while a sweep of the spiny or club-like 

 and horned tail would have been fatal to anything in its path. 



As in the case of so many other groups, little has yet been 

 learned regarding the history of the fglyptodonts during 

 the interval between the later Pliocene and the Santa Cruz ; 

 the intermediate formations have yielded many fglyptodonts, 



