1883. ] Geology and Paleontolog /. 69 
Tue NevaDA Bipep Tracks.—It is probable that the contem- 
poraneity of man with the horse and other extinct Pliocene 
mammals in Western North America will soon be satisfactorily 
demonstrated. The first evidence on the subject was furnished 
by J. D. Whitney, chief of the Geological Survey of California, 
in the case of the Calaveras skull, which was said to be taken 
from the gold-bearing gravel; and in several other cases subse- 
quently added. From the fact that scientific observers were 
never present at the unearthing of the remains of man and his 
The Carson Mammoth Tracks. 
works from this formation, the evidence has been generally re- 
garded as inconclusive. ‘(he gold-bearing gravel of California is, 
_ however, a very peculiar formation, and an object once buried in 
_ it, would carry such marks of its origin as to be quite recogniza- 
_ble. This was the case with the Calaveras skull when first dis- 
covered, as I am informed by Professor Verrill of Yale College. 
This gentleman states that the skull was partially filled and cov- 
ered with the hard, adhesive “cement ” so characteristic of the 
_ formation. 
I here refer to two observations of my own made in 1879, in 
