390 p. S. MARTIN 



tively on a Pleistocene vegetation map, unless one relies largely on 

 biogeographic data as Dillon (1956) has done. Topographic com- 

 plexity inevitably leads to considerable difficulties in large-scale 

 mapping of vegetation. Twelve major units on Leopold's very use- 

 ful vegetation map of Mexico (1950) suggest something of the 

 problem. 



Paleobotanical study of the Willow Creek flora of Santa Cruz 

 Island, California, revealed a latitudinal shift in Pseiidotsuga, 

 Cupressus, and Pinus of perhaps 440 miles, less than the 800 miles of 

 zonal displacement in eastern North America (Chancy and Mason, 

 1934). Studies of late Pleistocene fossil birds indicate an even less 

 drastic shift. "The avifaunas of the Carpinteria asphalt and of some 

 of the Pleistocene caves of northern and central California (Miller, 

 1937, 1939) indicate that the boreal avifauna extended 200 miles 

 farther south along the coast, at least, and 1,000 feet lower on the 

 interior mountains. Possibly even more extreme extensions occurred 

 in other parts of the Pleistocene" (Miller, 1951, p. 610). The latter 

 comment is crucial; either the Carpinteria and other Pleistocene 

 cave faunas are not of Full-glacial age or the avifaunal displacement 

 is discordant with that represented by the Willow-Creek flora. 

 Actually, neither deposit may represent maximum displacement of 

 the coldest period. 



The same logic can be directed toward the Rancholabrean biota of 

 the famous tar pits. While the living representatives of this assem- 

 blage typify environments subequal to those found today in the Los 

 Angeles basin (summary in Schultz, 1938), the spectacular finds of 

 extinct animals stamp the assemblage as late Pleistocene. In the 

 absence of C" dating or other absolute age estimate, it is futile to 

 urge any bioclimatic theory relating the Rancholabrean biota to 

 Pleistocene chronology. However, one suspects that certain bio- 

 geographers have assumed that the fauna is of Full-glacial age and 

 that it proves lack of climatic change at this latitude. Assumptions 

 about the cause of large-mammal extinction in this biota, as in 

 others, may be intertwined with climatic inference. In view of the 

 results of isotope dating of similar late Pleistocene faunas, it seems 

 we may anticipate an age postdating the Wisconsin maximum for the 

 Rancholabrean fauna. 



Except for Clisby and Sears' work in New Mexico, late Pleisto- 

 cene pollen studies have been confined to the Pacific Northwest and 



