1913] Stoner: Pleistocene Bone Deposits of Rancho La Brea 393 



tar the organic tissues decayed, leaving the bones disconnected 

 and free to move about in the pools. Movement may have been 

 caused by pressure and movement of the deposits above, or prob- 

 ably to a greater extent by the struggling of trapped animals 

 and by the expulsion of the gas coming to the surface. The 

 continual movement of the tar while it was in a liquid state 

 scattered the bones of all the animals and formed a heterogeneous 

 mass in which the parts of many different individuals were 

 mixed in all possible ways. In the center of the pocket the bones 

 were most numerous and so interlocked that much time was 

 consumed in untangling them. Toward the periphery of the 

 pocket the bones usually thinned out, and since they were em- 

 bedded in a more sandy matrix they were much more easily 

 extracted. 



Summary. — In the recent excavations it is clear that the bones 

 occur in rather deep, narrow pits; that during the accumulation 

 of these deposits the different tar pools commonly remained i 

 distinct, due to the slow exudation of the tar; that the pockets 

 represent a gradual accumulation built up along with the sur- 

 rounding Pleistocene deposits. It is further shown that a num- 

 ber of the pockets contained several tons of bones massed together, 

 representing thousands of individuals and scores of species. Since 

 the bones are found only in connection with the tar pools, it is 

 evident that their accumulation and preservation was due to the 

 presence of the tar. 



Transmitted June 9, 1913. 



