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University of California Publications in Geology [Vol.9 



OTTJS ASIO (Linnaeus) 



There occurs in the collection thus far reviewed a single specimen 

 of the tarsometatarsus of this species. The specimen is perfect in its 

 preservation and when compared with the corresponding bone of the 

 living species of the region. Otus asio bendirei, is seen to accord with 

 it in every particular as perfectly as though taken from the same 

 individual. No other remains of the species have yet come to light. 



BUBO VIRGINIANUS (Gmelin) 



Aside from Otus, the genus Bubo is the least commonly represented 

 of all the strigine genera recorded from the asphalt. However, among 

 the fifty thousand or more specimens of fossil birds from these beds, 

 there occur a goodly series of the tarsometatarsus as well as the other 

 more characteristic bones of the limbs, thus affording material for a 

 fairly complete study of variation in the Pleistocene phase of this 

 great owl. When the problem was first attacked, with smaller series 

 at hand, it was found that variation was so extensive and so abruptly 

 discontinuous that specific distinction seemed imperative. However, 

 after careful scrutiny of the equally extended series at the Museum 

 of History, Science, and Art at Los Angeles, and thus supplementing 

 the series in the University collections, curves were plotted which 

 showed practically uniform gradients for the grosser dimensions and 

 the ratios of dimensions. The Pleistocene Bubo was thus found to be, 

 like the Pleistocene Haliaetus, a form of very wide range of variation. 

 Like Haliaetus also, the series of asphalt specimens includes within 

 its limits two Recent geographic races, a southern smaller and a 

 northern larger race. Bubo virginianus pacificus of Southern Cali- 

 fornia grades up to the lower limits of the Pleistocene series, while 

 the larger B. v. saturatus is far surpassed by the larger specimens from 

 the asphalt. 



The horned owls from Rancho La Brea would present a difficult 

 problem in classification for the systematic ornithologist who readily 

 distinguishes in size as well as in color between the geographic races 

 of Bubo virginianus. The fossil species is distinguished from the 

 Recent by a character not held in common, i.e., great variability in a 

 fixed locality. Some students of geographic races have gone so far as 

 to assert that no fossil bird should be assigned to the same species as 

 a Recent form. In the absence of those external characters upon 

 which the ornithologist in large measure relies, and, in view of the 



