252 THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 
want of the necessary care. Some fine skulls, nearly perfect, were still in 
existence in the miners’ camps, near Sonora, when that region was first 
visited by the writer; but they were not to be bought at any reasonable 
price. Occasionally such specimens are carried to San Francisco and placed 
on exhibition, always at a great pecuniary loss to the exhibitors. Two fine 
heads from Horseshoe Bend, on the Merced River, were thus exhibited some 
years since, the owner believing them to be of fabulous value. So far as 
known to the writer, they did not find their way into any public museum, 
where they would be likely to be cared for and preserved. 
By far the larger number of specimens collected in California or elsewhere 
in the United States belong to the common, well-known species, MZ. Americanus. 
But besides this, there appear, according to the latest expressed opinion of 
Dr. Leidy,* to have been at least three others which inhabited this continent: 
these are MW. mirificus, M. Andium, and M. obscurus. Of the first of these, 
remains have been found by Dr. Hayden, in association with an abundance 
of those of other species of extinct animals, in the Pliocene formation of 
the Loup Fork of Platte River. Remains apparently identical with the 
South American JZ Andiwn have been discovered in Central America, and 
the fourth species, JZ. obscurus of Leidy, is known only by specimens col- 
lected in California and New Mexico. For a full account of the relations of 
these different species, their mode of occurrence, and their distribution, many 
different works must be consulted. The species which interests us particu- 
larly, next to MZ. Americanus, is M. obscurus, and the specimens of this which 
have been found in California are described and figured in Dr. Leidy’s “ Con- 
tributions, &c.”t There are two localities, so far as known to the writer, 
where the remains of JZ obscurus have been found, one in the Coast Ranges 
and one in the foot-hills of the Sierra. The Coast Range locality is Oak 
Springs, Contra Costa County; the other is at Dry Creek, in Stanislaus 
County. Both of these were discovered by Dr. Yates. There is also a cast 
in plaster of a mastodon tooth in the Museum of the Philadelphia Academy, 
the original of which is supposed to have been found in the Miocene of Mary- 
Jand. The specimen from thé foot-hills of the Sierra was at first considered 
by Dr. Leidy as distinct from the one obtained in Contra Costa County, and 
was described by him under the name of JZ. Shepardi; but he afterwards 
included it with JL odscurus. He says, in reference to this matter and to the 
* Contributions, &., p. 231. 
t l.c., pp. 231-287, and Plates XXI. and XXII. 
