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FOSSILS IN THE GRAVEL: 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- 
voleanic 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 ZR. hesperius.™ 
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 Lt. occidentalis, 2 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.” 
Of the other specimen, from Douglass Flat, Dr. Leidy’s notes, ftwnished 
the 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. 
