1912] Miller: Pacific Coast Avian Palaeontology 75 



LIST OF BIRDS FROM HAWVER CAVE. 



*Nettion carolinense (Gmelin). '*Geranoaetus melanoleucus Auct.f 



*Oreortyx picta (Douglas). *Colaptes cafer (Gmelin). 



*Lophortyx calif ornica (Shaw). *Cyanocitta stelleri (Gmelin). 



*Meleagris, sp. *Corvus corax Linnaeus. 



*Cathartes aura (Linnaeus). *Eup'hagus cyanocephalus (Wag- 

 *Catharista shastensis Miller. ler). 



*Archibuteo ferrugineus (Lichten- 

 stein). 



* An asterisk indicates that the species is extinct 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, 11 who bases his conclusions on per- 

 sonal observation and upon the opinions of Arnold, Orcutt, 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 increas- 



11 Merriam, J. C., Mem. Univ. Calif., vol. 1, No. 2, pp. 199-213, 1911. 



