1912] Miller: Pacific Coast Avian Palaeontology 75 
List oF Birps FROM HAWVER CAVE. 
*Nettion carolinense (Gmelin). “Geranoaétus melanoleucus Auct.? 
*Oreortyx picta (Douglas). *Colaptes cafer (Gmelin). 
*Lophortyx californica (Shaw). *Cyanocitta stelleri (Gmelin). 
*Meleagris, sp. *Corvus corax Linnaeus. 
*Cathartes aura (Linnaeus). *Euphagus eyanocephalus (Wag- 
*Catharista shastensis Miller. ler). 
*Arehibuteo ferrugineus (Lichten- 
stein). 
* An asterisk indicates that the species is extinet or no longer found 
in this region. 
Rancho La Brea—The Rancho La Brea beds constitute one 
of the most unique and at the same time one of the richest of 
Pleistocene deposits in the west; unique because in the entomb- 
ment of remains the factor of chance has been reduced to a 
minimum by the presence of an attractively baited and auto- 
matic trap; rich because the trap was insatiable in its demands, 
because the material was promptly immersed and preserved in 
semi-fluid asphalt, and because of the fact that the trap was 
almost continually operative, it would seem, for a considerable 
period of time. 
According to Merriam, who bases his conclusions on per- 
sonal observation and upon the opinions of Arnold, Oreutt, and 
other geologists, crude asphaltic oil from the underlying Fer- 
nando shales, here gently upfolded, has been forced to the sur- 
face through cracks or chimneys in these folded strata to ac- 
cumulate upon the surface as more or less extensive oil pools. 
This heavy oil, under the influence of sun and wind, underwent 
a process of natural distillation, becoming more and more viscid 
until in the larger accumulations it was sufficiently tenacious 
to entrap and hold the largest mammals of the region, Elephas, 
Mastodon, and Paramylodon. As pointed out by the same 
author, additions to these lenses of asphalt took place at the 
center as fresh oil rose through the chimneys from below; at 
the same time dust and sand drifted over and obscured the 
firmer asphalt of the margins. These two factors combined to 
bring about a most deceptive condition in the mass by leaving 
the periphery fairly firm and yet permitting a gradually inereas- 
11 Merriam, J. C., Mem. Univ. Calif., vol. 1, No. 2, pp. 199-213, 1911. 
