1918] Stock: The Pleistocene Fauna of Hawver Cave 



477 



ECOLOGICAL CONSIDERATIONS 



The foregoing comparisons between the Pleistocene fauna of Haw- 

 ver Cave and the fauna now living in the vicinity of the fissure 

 indicate that the conditions which prevailed during accumulation of 

 the fossil material were for the most part similar to those now prevail- 

 ing in this region. Then, as now, the region of the cave deposit was 

 tenanted or at least traversed by plains and forest types. This 

 mixture of forest- and plains-dwelling forms has been noted also by 

 Sinclair for the Pleistocene fauna of Potter Creek Cave. Types fre- 

 quenting or preferring the open plains are represented at Hawver 

 Cave by Equus, Bison, and presumably by Mijloclon and the sabre- 

 tooth tiger. At Potter Creek Cave there occur besides Equus and 

 Bison, a camelid and Elcphas; while in Samwel Cave only Equus and 

 Elcphas, among the large forms, are indicative of such a habitat. 



It is to be noted that the Pleistocene fauna of Hawver Cave came 

 more under the influence of the plains environment than did the fauna 

 of either Potter Creek Cave or Samwel Cave. This is suggested also 

 by the absence of Oreaninos from the fissure in Eldorado County and 

 the presence of this form in the Shasta caves. The present elevation 

 of Hawver Cave above sea-level and the nature of the physiography 

 in the vicinity of the deposit indicate that the region is not now in- 

 accessible to forms living in the Great Valley of California. The fact 

 that the prong-horn antelope and the dwarf elk are known to have 

 ranged into this region, either during the present period or within 

 the past fifty years, supports this contention. During the Pleistocene 

 such plains-types as the bison, Equus and Mylodon were represented 

 in the region. The range of Mylodon is restricted less by altitude and 

 ruggedness of country than is usually supposed, for remains of this 

 form have been found at great elevation in the Peruvian cordilleras. 



Euccrathcrium, Megalonyx and Nothrothcrium may be cited as 

 characteristic of the belt in which Hawver Cave is situated. These 

 forms probably ranged even higher in the Sierras than is indicated 

 by their presence at Hawver Cave, but their size and weight no doubt 

 prevented them from ranging to the summits. The ground-sloths 

 Megalonyx and Nothrothcrium apparently proved to be easy prey 

 for the sabre-tooth tiger, for so far as known these forms were not 

 protected by an armor of dermal ossicles. In contrast to the megalony- 

 chids is the genus Mylodon, in which t} r pe the ossifications in the skin 

 are well developed and serve admirably to shield the animal from 

 stabbing attacks of the machaerodonts. 



