INTRODUCTION 



Of the numerous occurrences of animal remains representing prehistoric 

 life on the North American continent, the locality at Rancho La Brea furnishes 

 one of the most nearly complete pictures of the fauna of a given region at a 

 given period that has thus far been obtained. When all of the data have been 

 gathered through intensive study of this field, and when the facts thus assem- 

 bled have been interpreted, we shall have gone far toward reaching an under- 

 standing of the biologic and climatic conditions obtaining in the Los Angeles 

 region during one phase of Pleistocene time. So significant do the results of 

 a study of this fauna appear in relation to the general problem of the Pleisto- 

 cene, that it seems desirable to bring together the conclusions obtained in work 

 on all phases of the assemblage of life forms here represented. 



Since receiving the first specimens from Rancho La Brea, in December, 

 1905, the Department of Palaeontology at the University of California has been 

 almost continuously engaged in a study of this most alluring field. Some of the 

 results obtained have already been presented in brief papers by J. F. Bovard, 

 L. H. Miller, W. P. Taylor, and the writer. Other articles based on material 

 furnished by the University have been written by Win. J. Sinclair and by 

 Fordycc Grinnell. The present paper is the first of a series of publications 

 in which it is planned to present in full the results of work on all of the groups 

 represented in the Rancho La Brea fauna. It is not to be presumed that all 

 of the facts relating to any of the groups discussed are yet discovered, and the 

 writing of the last word on the Rancho La Brea fauna will probably fall to 

 investigators of a later generation. It is, however, hoped that at this present 

 stage of progress a considerable number of the principal items of information 

 may be brought together; and that from these we may construct at least the 

 foundation for more extensive work such as naturally follows any initial 

 investigation. 



In studying the fauna obtained from the Rancho La Brea Beds the writer 

 has been assisted by many persons who have been interested in the work. Par- 

 ticular acknowledgment is due to Madam Hancock Ross and to Mr. Allan 

 Hancock for their courtesy in permitting the University to carry on its exca- 

 vations in this interesting field. To Mr. F. M. Anderson and Mr. W. W. Orcutt 

 the writer is indebted for the original information which led to "so many dis- 

 coveries. Mr. Anderson presented his first collection to the University, and 

 Mr. Orcutt permitted the use of his material for study. 



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