172 /. C. Russell — Expedition lo Mount St. Elias. 



were submitted to Dr. W. H. Dall, who kindly identified them 

 as follows : 



Mya arenaria, L. ; 



Mytilus edulis, L. ; 



Leda fossa, Baird, or L. viinuta, Fabr. ; 



Macoma inconspicua, B. and S. ; 



Cardium islandicum, L. ; 



Litorina atkana, Dall. 



All of these species are stated by Dall to be still living in the 

 oceanic waters of Alaska. The very recent age of the rocks in 

 .which they occur is thus established. 



Figure 8 — Faulted Pebble from Pinnacle Pass. 



In strata closely connected with the layers in which these shells 

 were found there occur many fine leaf impressions, a few of 

 which were brought away. These have been examined by Pro- 

 fessor L. F. Ward, who has identified them with four species of 

 Salix, closely resembling living species. The report on these in- 

 teresting fossils forms Appendix D. 



The age indicated by both invertebrates and plants is late Ter- 

 tiary (Pliocene) or early Pleistocene. This determination is of 

 great significance when taken in connection with the structure 

 of the region, and shows that the mountains in the St. Elias 

 region are young. 



Not only was a part, at least, of the Pinnacle system deposited 

 during the life of living species of mollusks, but also the whole 

 of the Yakutat series, the stratigraphic position of which is, if 

 my determination is correct, above the Pinnacle system. After 

 the sediments composing the rocks of these two series were de- 



