82 University of California Publications in Geology [Vo L - 7 



Rodeo Pleistocene. Almost nothing has been recorded con- 

 cerning this formation. The region has been repeatedly visited 

 by parties from the University of California and the Pleistocene 

 age of the beds definitely established. 



The single specimen of bird remains from the locality was 

 picked up at the base of the exposure by Professor J. C. Mer- 

 riam with parts of the matrix of the Pleistocene beds still adher- 

 ing to it. The bone is a perfect tarsometarsus of average size. 



SINGLE SPECIES FROM EODEO PLEISTOCENE. 

 2Echmophorus occidentalis (Lawrence). 



PRESENT PHYSIOGRAPHIC AND GEOGRAPHIC RELATIONS OF THE 



WEST AMERICAN REGIONS IN WHICH FOSSIL AVIAN 



REMAINS ARE KNOWN 



The nine localities referred to above have yielded several 

 thousand specimens in all. Only five of these specimens, repre- 

 senting three species, are from deposits older than the Pleisto- 

 cene ; hence we may consider our knowledge as practically limited 

 to that age. Since also the systematic groups larger than the 

 species display in the case of birds such remarkable longevity, 

 time relations between the several Pleistocene horizons become 

 of minor importance except as we learn of variations in climate 

 during that period. 



There is on the other hand an advantage to be derived from 

 the approximate contemporaneity of the deposits. The entomb- 

 ment of many specimens at about the same time under a variety 

 of conditions and in a number of different localities gives us 

 an unusually accurate conception of the avifauna of that time. 

 The Fossil Lake deposits yield mainly those species to be found 

 about open, shallow lakes; the caverns are so located as to h 

 entombed those species which inhabit lower mountainous coun- 

 try ; the Rodeo Pleistocene consists of seashore accumulation ; the 

 Rancho La Brea beds a.re the result of a peculiarly diverse com- 

 bination of circumstances which led to the trapping of open- 

 plains birds with a preponderance of raptorial species. 



The asphalt beds lie in latitude 34 N, on the coastal side of 

 the Santa Monica Mountains within a few miles of the sea and 



