256 THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
as has been repeatedly noticed to be the case with the mastodon remains. 
Further remarks on this point and on the probable relative geological age of 
the mastodon and elephant may be found in the following section. 
Next to those of the mastodon and elephant, the most abundant, fossil 
remains found in the gravel region are those of the horse, and of this animal 
several species have been recognized by Dr. Leidy among the specimens col- 
lected from different parts of the State and submitted to him by the Geologi- 
cal Survey. It seems proper to publish in full the notes furnished by him 
in regard to the equine remains examined, although some years have elapsed 
since they were written. These notes do not appear to have been rendered 
any the less valuable by what has since been published on this subject. They 
will be followed by some general remarks on the probable geological position 
of the different species mentioned, which will be introduced when discussing 
the age of the human remains discovered in the same deposits with the 
various animals which have been described. 
Equus excelsus, Lerpy: Proc. Ac. Nat. Sci., Phila. 1858, 26. 
Equus occidentalis, Lrrmpy: Ibidem, 1862, 94. 
An extinct species supposed to be different from other North American species, and about the 
size of ordinary varieties of the recent domestic horse. It is indicated by the following specimens : 
a. The greater portions of both jaws of an individual of mature age. The specimens are thor- 
oughly imbued with bitumen, and were obtained near Buena Vista Lake.* 
The portions of the upper jaw contain the incisors, canines, and the anterior four large molars 
of the left side. The teeth resemble in their size and relationship those of the living horse. The 
course of the enamel lines on the triturating surfaces of the molars presents an extreme condition 
of simplicity. The bottom of the principal internal valley is devoid of the inflection of enamel 
seen in the recent horse, and in this respect the fossil teeth resemble more those of the ass. 
The portions of the lower jaw contain all the teeth of both sides except one last molar. The 
teeth present nothing peculiar distinguishing them from those of the recent horse. 
b. Portion of the left ramus of a lower jaw of another individual from the same locality. It 
belonged to an older but somewhat smaller animal, and like the preceding specimens is imbued 
with bitumen. It contains the anterior five molars. 
ce. An isolated upper molar, from the same locality and in the same condition. It exhibits the 
peculiarities already mentioned in the series of upper molars. 
The collection of the Academy of Natural Science also contains a portion of an upper jaw 
with the anterior five molars, from the same locality and in the same condition, presented by 
Dr. George H. Horn. The teeth likewise exhibit the peculiarities above mentioned, distinguishing 
them from those of the recent horse. 
d. An isolated upper molar, from auriferous clay, twenty feet below the surface, Columbia, 
Tuolumne County. It is a second of the series, is hardly changed in texture, and is only partially 
stained with iron. The tooth exhibits the same peculiarities as the upper molars above indicated. 
e. Two upper molars, from different individuals, with no locality indicated [but probably from 
Sonora]. They both exhibit the peculiarities above mentioned. 
* The exact locality is believed to be the “Sta. Maria Oil Springs,” about twelve miles northwest of 
the north end of Buena Vista Lake. 
