68 THE FOSSIL SLOa^II AT ma BONK CAVE, TENN. [Jan. 15, 



its interstices, we abandoned it where the configuration of the cave 

 walls, widening as we went down into a crevice of unknown depth 

 (see Fig. 4), rendered further work under the circumstances hopeless. 

 We left with the reasonable inference that a depth of five, ten or fif- 

 teen feet would have laid bare the whole bottom, as it had been laid 

 bare elsewhere in the gallery. Doubtless the process of drying, 

 which succeeded the deposition of the layer by water, had broken 

 it into lumps, between which the upper refuse, as remarked before, 

 had penetrated, thus adulterating it without obscuring the fact that 

 in its true constitution, for the eighteen inches examined, it con- 

 tained no trace of man or animals. 



Allowing the dust to settle for the last time, we turned away from 

 the mysterious spot, and, threading our way wearily through the 

 chilly gallery, came with sudden shock upon the dazzling glow and 

 severe heat of a southern evening. With difficulty we toiled home- 

 ward, resting often in the warm woods. 



At the last remaining point of significance we had examined layers 

 which probably present all the evidence that will ever be collected 

 as to the antiquity of the fossil sloth of Big Bone cave. 



Let paleontology enlighten us as to the probable character and 

 habits of this animal which we must reasonably regard as one of 

 the common inhabitants of the American forest in Pleistocene 

 times. Comparing the large vertebrae, the skull, the proportion- 

 ately shorter claws and stouter limbs with the skeletons of the existing 

 South American sloths, as here shown (thanks to the kindness of 

 Dr. H. C. Chapman), we may well disbelieve that this animal hung, 

 like the latter, back downward for days upon a single bough, or 

 lagged in one tree or grove until moss formed upon its fur. 

 How shall we imagine the creature, weighing from twelve to sixteen 

 hundred pounds, moving from tree top to tree top in any known 

 North American forest, when on the blowing of wind, according to 

 the saying in Brazil, sloths travel. On the contrary, as the contin- 

 ual falling of so large an animal by the breaking of boughs is not 

 to be imagined, we must deny the creature a strictly arboreal life, 

 rather supposing, with Prof. Cope, that the boughs came down to the 

 sloth than that the sloth went up to the boughs. In place of 

 moss-covered clumps of motionless fur not easily distinguished 

 from leaves, that a keen eye recognizes in South American 

 tree tops, we fancy animals inhabiting the earth and proclaim- 

 ing their presence by the crash of saplings and outlying boughs, 



