450 CARNEGIE INSTITUTION OF WASHINGTON. 



Further important laboratory work has involved very extensive 

 selection, assembling, and measurement of the great collections of 

 Rancho La Brea material at the Museum of History, Science and 

 Art of Los Angeles and at the University of California. This work 

 has been done under the direction of Dr. Stock. It has involved a 

 long-continued and painstaking review of the collections and has 

 resulted in the securing of extraordinarily fine specimens for study. 

 There has also been prepared, for final comparative work, the most 

 extensive system of measurements ever based upon a collection of 

 fossil mammals, so far as the writer is aware. 



Special difficulties in the way of assembling the Rancho La Brea 

 collections are found in the fact that the individual bones of many 

 skeletons have been interwoven in an almost inextricable tangle, so 

 that the parts of a single skeleton are often found scattered over the 

 whole length, breadth, and depth of a given asphalt pit. In the 

 present case, involving the study of hundreds of thousands of bones, 

 the difficulty of adequate assembling has been enormously increased. 



The laboratory studies have involved further the preparation of 

 large series of illustrations comprising several thousand drawings and 

 many hundreds of photographic plates, which must accompany the 

 monographic studies. The necessity for such illustration lies in the 

 fact that much of the material available is not accessible for other 

 students, and it is therefore incumbent upon the authors interpreting 

 this fauna so to illustrate the work as to convey the clearest 

 meaning concerning the materials described. For a number of the 

 papers illustrations are also planned which will represent as accurately 

 as possible the approximate outlines of the living creatures whose 

 skeletons are under examination. It is not intended that these out- 

 lines shall convey more than the sketch form, such as is indicated 

 by the character of the bones and the evidence of muscular attach- 

 ment. This series of studies has been carried forward in most satis- 

 factorily by Mr. Charles R. Knight. 



The results of work completed within the past year are embodied in 

 seventeen papers prepared by members of the small group cooperating 

 in the conduct of investigations described above. Of these contribu- 

 tions, eight are already in press and three or four will have been issued 

 before this report is printed. Inasmuch as the list of titles covering 

 publication does not fall within the period fixed for the date of the 

 annual report, the titles are held for inclusion in the annual report 

 of 1922. 



As a summary of conclusions covering work of the year it may be 

 stated that the investigations have contributed specifically to the ad- 

 vancement of research in the following directions: 



1. Completion of two monographs on the remarkable Pleistocene 

 fauna discovered at Rancho La Brea. 



