EXPLORATION IN ALASKA IN I907 — GILMORIC 23 



by Mr. Maddren on the Porcupine and Old Crow rivers, from the 

 fact the fossils did not become more abundant on the bars as we 

 went upstream. On some bars many fossils would be found, while 

 others would yield only a single specimen. The varying degrees of 

 preservation exhibited by the specimens points to the conclusion that 

 the source of supply is diverse and not one large deposit. The 

 writer is inclined to the opinion that the fossils found on the bars 

 have been washed out of the silt banks along the stream and trans- 

 ported to their present resting places largely by the action of the 

 water. 



The finding of abundant remains on the bars of a stream that is 

 cutting elevated silts does not necessarily lead to the conclusion that 

 all of the specimens found there have come from the headwaters of 

 that stream, for we know that scattered bones occur in the silt depos- 

 its, and it appears that the bones brought down from far upstream 

 may be augmented in numbers by those washed out of the silts along 

 its course. 



The following list gives the fauna of this area as represented by 

 the scattered bones collected : 



Blephas primigenius. 



Bison. 



Bquus. 



Ursus. 



Alee. 



Castor. 



YUKAKAKAT RlVER 



Although fewer fossils were collected along this stream, the pre- 

 vailing conditions as to their occurrence were found to be similar 

 in most respects to those observed on the Nowitna River. 



The following forms were recognized : 



Blephas primigenius. 

 Bison. 



Klaus hkakat River 



A locality on this stream some three miles inland from the Yukon 

 was visited. Here the bluffs present nearly perpendicular faces from 

 sixty to eighty feet in height, the lower parts of which are com- 

 posed of reddish cross-bedded gravels, varying from fine to very 

 coarse and unconformable with the overlying silt. The silt shows no 

 traces of stratification and is solidly frozen. Back from the bluff 

 is a level tableland, bordered on all sides, except that adjacent to the 

 river, by low hills. It was at this locality that Mr. Collier in 1902 



