18 BUREAU OF AMERICAN ETHNOLOGY [BULL. 66 
the excavators obtained all possible information as to the nature of the deposit 
in which the specimen was found, and every bone appearing in the deposit was 
saved. The final results of the work give us a complete map 1 of the deposit 
and full list of the animal remains from the two chimneys, with their situa 
tion in the chimneys. 
****** 
Purely geologic evidences of age are often exceedingly difficult to obtain in 
asphalt deposits, owing to the peculiar mode of accumulation, and the possi 
bility of movement in the deposits after they are once formed. The asphalt is 
a residue from evaporation of oil. It accumulates either on the surface of the 
ground or in the midst of other strata into which it has soaked or poured. 
Even after the asphalt deposit has formed, the nature of the viscous material 
makes possible considerable movement in many directions within the mass 
and consequent change of position of any materials in it. 
The deposits in which fossil remains have been found at Rancho La Brea 
are evidently in part layers formed on the surface, and in part pipes, pockets, 
and chimneys through which oil came up from deeply buried strata. The 
source of the asphalt or oil is a deep-lying formation, which is considerably 
folded, and is covered by approximately horizontal layers of clayey and sandy 
strata washed in from higher land not far away. Oil and gas have been seeping 
through the superficial horizontal deposit for a very long period, and have 
formed more or less definite channels or pipes along lines of least resistance. 
In some cases these pipes have evidently enlarged themselves locally to chim 
neys several feet in diameter. 
At pit No. 10, in which the human remains were discovered, the asphalt de 
posit consists of two pipes or chimneys connecting with surface flows above. 
The chimneys arise below from a large dome-shaped asphaltic reservoir. This 
dome may be an old surface pool now buried and forming a part of the pas 
sageway for further upward movement of oil ; or it may be an enlargement of 
a chimney that was originally very much smaller. 
The asphalt in the chimneys and in the dome in pit 10 was largely a soft, 
viscous mass containing a high percentage of sand, and including in some re 
gions many angular lumps of hard, weathered asphalt. The contents of the 
chimneys are entirely unlike the surrounding soil or rock. The material 
through which the chimneys pass is not homogeneous, but is composed of ap 
proximately horizontal strata of clay, sand, and gravel, with a small inclusion 
of asphaltic material in most places. The contact between the chimneys and 
the matrix through which they pass was everywhere sharply marked. 
******* 
Bones of birds and mammals were abundant in both chimneys. In the 
south chimney, which is wide above and narrows sharply below, large bones 
are found only above the narrowing of the pipe. In the large reservoir below 
the chimneys only small bones appear, and these were found only in a limited 
space near the point of union of the lower reservoir and the two chimneys. 
The distribution of bones shows conclusively that they came from above, and 
were not carried up from the depths with ascending oil. 
The total number of specimens found in the chimneys was large, and will 
aggregate several thousand. These bones represent a considerable variety of 
mammals and birds. They include be;ir, coyote, a wolf of the timber-wolf type, 
skunk, weasel, horse, antelope, rabbit, pocket gophers, field mice, eagles, owls, 
vultures, crows, and many other forms. 
The fauna from the two chimneys in pit 10 is in general like that of Cali 
fornia at the present time. It differs greatly from that of the pits in which 
