FOSSILS IN THE GEAVEL : UNDER THE BASALT. 



243 



volcanic series, carried far from their original resting-place, and deposited in 

 such a position that they seem to belong to the present epoch. 



In view of the above considerations, it seems reasonable, in endeavoring to 

 find a line of demarcation, as indicated by fossil remains, somewhere in the 

 gravel and volcanic series, to inquire what is positively known to have been 

 found in strata lying undisturbed under the basalt ; or, at least, so far down 

 in the volcanic formations as to preclude any possibility that the object in 

 question could have found its way down from a superficial deposit of post- 

 volcanic age. It will be well, therefore, in the first place, to take up the 

 material collected by the Geological Survey, and investigated by Dr. Leidy, 

 and ascertain what has been discovered unquestionably older than the epoch 

 of the eruption of the basalt. 



The number of species in regard to which the evidence is clear that they 



are prior in age to the eruption of the basalt is not large. 



The most im- 



portant localities are those of Douglass Flat, Chili Gulch, and the Tuolumne 

 Table Mountain, the position of which has already been sufficiently explained. 

 From Douglass Flat and Chili Gulch remains of a species of rhinoceros were 



obtained, which have been described by Leidy under the name of E. hespcrius. 

 In both cases the specimens exhibited a considerable portion of the jaw with 

 a number of teeth. That from Chili Gulch consisted of the right side of 



■ 



the lower jaw, without the ascending portion, and with the symphysial por- 

 tion of the opposite side. It contained the true molars, the fangs of four 

 premolars, one lateral incisor, and the fang of the other, and the alveoli of the 

 internal incisors. The form of the jaw is nearly like that of the corresponding 

 portion of the Indian rhinoceros, and the formula of dentition the same as in 

 that species. The size of the species, as indicated by the jaw, is nearly that 

 of 11 occidentalism a common species of the Mauvaises Terres, described by 

 Leidy, and considered by him to be from half to three fourths as large as the 

 living Indian species. Of the Chili Gulch jaw Dr. Leidy remarks : " The 

 specimen so closely resembles in its general aspect and state of petrifaction 

 the Mauvaises Terres fossils of White River, Dakota, that it would have been 

 viewed as one, if the locality from which it was obtained were not known.' 



# 



th 



Of the other specimen, from Douglass Flat, Dr. Leidy's notes, furnished 

 ie writer, give the following account : " This second specimen is remark- 

 able on account of its condition of preservation, so totally different from the 

 other. It consists of a portion of the left ramus of a lower jaw of a, young 



* Extinct Mammalia of Dakota and Nebraska, p. 230. 



