Port Clarence Limestone, Ataxia. 343 



"There is little evidence upon which to base the opinion that 

 Locality 7 is younger than Locality 8, and the best possible 

 explanation of the sequence appears to be the presence of a fault 

 somewhere between 6 and 7." 



It will be noted that Dr. Walcott and Mr. Ulrich fully agree 

 on the important points that the faunule of station 8 is of 

 Upper Cambrian age, and that it is older than the faunule at 

 station 6. Whether the latter faunule should be placed in the 

 passage beds between the Cambrian and Ordovician, as sug- 

 gested by Dr. Walcott, or entirely in the Lower Ordivician, as 

 held by Mr. Ulrich, is not a matter of great moment in this 

 connection. The order of succession of the two faunnles on 

 which they agree, however, necessitates the postulation of 

 structural features between the mouth of Lost River and 

 Brooks Mountain which were not previously suspected. In 

 view of the extremely complicated structure which Smith* 

 has shown to exist in a portion of the Seward Peninsula, it is 

 perhaps not profitable to attempt in the light of our present 

 knowledge of the structure of the York Mountain region to 

 state just what these structural features are. 



Fucoid-like impressions are, abundant between the beds of 

 station 6 and the coast, apparently 200 feet or more above 

 them stratigraphically. Similar impressions were observed 

 by Collier and Washburne, and are mentioned by Ulrich, f 

 who had some doubt as to their organic nature, in his report 

 on their collection. In addition to the "fucoids" the Wash- 

 burne collection contained fossils which Ulrich:}: compared with 

 the following species : 



Stromatoeerium rugosuin 

 Hormotoma bellicincta 



Trochontma sp. 



Cyrtoceras ? 

 En doceras? 



These fossils were collected near the mouth of Lost River and 

 appear to belong to the same general horizon as the fauna 

 from station 6. They represent with it an early Ordovician 

 horizon. Knopf§ also obtained some fragmentary gasteropods 

 in the Lost River valley which appeared to represent an 

 Ordovician horizon. 



The next fauna in the order of age which is known in the 

 Port Clarence limestone occurs in limestones on the Don River, 

 about 9 miles from the coast. The first collection from this 



* Smith, P. S., Geology and Mineral Kesources o1' the Solomon and Cassade- 

 paga quadrangles: Bull. U. S. Geol. Survey, No. 433, pp. 1-234-, 1910. 

 -t-Bull. U. S. Geol. Survey, No. 328, p. 78, 1908. 

 % Bull. U. S. Geol. Survey, No. 328, p. 78, 1908. 

 § Bull. U. S. Geol. Survey, No. 358. 



