CAVE DEPOSIT GIDLEY. 285 



In contemplating this list one must bear in mind that the fossil 

 and living forms compared, with few exceptions at least, are not 

 identical species, but these fossil forms doubtless in life would have 

 closely resembled their present-day relatives in general appearance 

 and probably in habits. 



The especially interesting phase of this fauna of the Cumberland 

 Cave deposit, then, is the association of remains of animals whose 

 modern relatives are now living under widely varying climatic 

 conditions, as well as distant geographic ranges. And in referring 

 to the lists enumerated above one might well ask what sort of 

 climate prevailed in the western Maryland region during that por- 

 tion of the Pleistocene in which this deposit of bones was being 

 formed ? 



Crocodiles or alligators are not known to have ever existed outside 

 of tropical or subtropical climates, and, moreover, cold-blooded 

 saurians could not have inhabited a locality where the temperature 

 was accustomed to fall much below the freezing point. The present 

 day tapirs and peccaries also are confined to tropical and subtropical 

 localities. The presence of these creatures then, and especially the 

 crocodile, seem strongly to indicate a warm climate for our cave-de- 

 posit fauna. On the other hand, the wolverine is always considered 

 a boreal animal, normally associated with cold climate conditions 

 and martens and minks, too, for the most part, now inhabit northern 

 or at least temperate zones, while the little picas or coney rabbits, 

 to-day are found living only in the higher altitudes of the Rocky 

 Mountains or some of the colder regions of Asia and eastern Europe. 

 The presence, therefore, of these animals may be taken as almost 

 equally strong evidence of cold climatic conditions. 



How, then, may one account for this intermingling of animals of 

 such widely varying climatic zones? There are at least three pos- 

 sible explanations. The first, and most unlikely perhaps, would be 

 to suppose that the animals of the Pleistocene sufficiently differed 

 in habits from their living relatives as to render comparisons en- 

 tirely untrustworthy; or, second, that the accumulated fossil bones 

 of this deposit represent a lapse of time sufficient for a gradual 

 local change in climate, from mild subtropic to boreal or arctic, con- 

 ditions (or vice versa), accompanied by a gradual and appropriate 

 change of faunas ; or third, and to me the most likely supposition is 

 that the average temperature of the general region, at least of the 

 lowlands and valleys, was warmer then than now, while the mountain 

 ranges and peaks in the vicinity, being less worn down by erosion 

 were probably much higher and therefore colder, possibly even snow 

 capped. 



Such a condition would naturally bring the boreal faunas much 

 farther south than we now find them, while the valleys and lowlands 



