468 THE AGE OF MAMMALS 



ficus and E. occidentalis. Among the equine remains are hock bones, or 

 calcanea, of exceptional size, indicating the presence of a horse of large 

 dimensions; and there were also small, fine-limbed types of horses. The 

 elephant teeth chiefly belong to the Columbian mammoth, presenting about 

 twenty enamel folds in a space of ten inches. One molar approaches the 

 true northern mammoth (E. primigenius) in the possession of twenty-five 

 folds in a space of ten inches. At the opposite extreme is a tooth which 

 exhibits folds varying from thirteen to fifteen in ten inches, which appears 

 to indicate the presence of the imperial mammoth (E. imperator). (See 

 Fig. 190.) The identifications of E. primigenius and E. imperator in this 

 fauna, however, await final confirmation. This would be the first positive 

 association of these species with the Megalonyx, or Mylodon fauna in early 

 mid-Pleistocene times. 



Upper Lake Lahontan beds. — The special importance of the few mam- 

 malian remains found in the Lake Lahontan deposits is that they are 

 definitely recorded geologically. Proboscidean bones are found in the 'in- 

 termediate gravels' in the Lahontan basins (equivalent to the gravels of 

 the inter-Bonneville epoch) , also in the ' Upper Lahontan beds ' (equivalent 

 to the 'white marl ' of the Bonneville). There is no doubt that the fossils 

 were all derived from the ' upper lacustral beds ' ^ ; they include an elephant 

 {? E. columbi), a horse, a bison, and a llama, none of which has been iden- 

 tified specifically. In the same ' upper lacustral clays ' an obsidian spear- 

 head was obtained (see p. 448), positively associated with proboscidean 

 remains; there is no doubt that the mammalian remains all belong to the 

 time of the last great rise of the lake (op. cit. p. 273). The pres- 

 ence of bison would appear to indicate that these ' upper lacustral clays ' 

 and the fauna which they contain are of more recent date than the Silver 

 Lake Equus beds, with which they were correlated on insufficient grounds 

 by Gilbert in his Bonneville memoir.^ 



Port Ketinedy Cave of Penfisylvania is situated on the right bank of the 

 Schuylkill River, two miles below Valley Forge, Pennsylvania (Fig. 194, 4). 

 As studied by Cope ^ and Mercer * this locality has yielded sixty-four 

 species of mammals, of which twelve are known to be still in existence and 

 forty to be extinct ; the ratio of recent to extinct forms would, however, be 

 greatly increased by more careful comparison and more conservative deter- 

 mination. The animals were apparently collected here by a series of fresh- 

 water inundations, carrying Avith them the clay, stones, and earth of neigh- 

 boring levels, and the bones of mammals separated and scattered by 



' Russell, I. C, Geological History of Lake Lahontan, a Quaternary Lake of North- 

 western Nevada. Monogr. U.S. Geol. Surv., Vol. XI, 1885, p. 238. 



2 Gilbert, G. K., Lake Bonneville. Monogr. U.S. Geol. Surv., Vol. I, Washington, 1890. 



^ Cope, E. D., Description of Some Vertebrate Remains from the Port Kennedy Bone 

 Deposit. Proc. Acad. Nat. Sci. Phila., Vol. XL 1876, Pt. 2, pp. 193-267. 



* Mercer, H. C, The Bone Cave at Port Kennedy, Pennsylvania, and its Partial Exca- 

 vation in 1894, 1895, and 1896. Jour. Acad. Nat. Sci. Phila., Vol. XI, Pt. 2, 1899, pp. 269-288. 



