40 The Siskiyou Island. 



geological history all over the world at the 

 close of the Cretaceous period. 



Bivalves of the, Venus and Mactra families 

 were also abundant, and smaller shells in in- 

 creasing abundance filled those old beaches 

 with beauty and wealth of scientific materials. 



In our narrative of the greater geological 

 changes along the Pacific coast we found the 

 gathering forces of a great geological revolu- 

 tion were taking form and direction, destined 

 to change the whole western face of the con- 

 tinent. The colossal sea dyke referred to in 

 the previous chapter as the Cascade barrier 

 was slowly rising from the bed of the ocean, 

 its line of uplift falling a little eastward of our 

 Siskiyou island and ultimately resulting in 

 connecting that island with the main land. 

 The point was reached of the permanent sepa- 

 ration of the two. islands by the upfold of the 

 Cascade barrier the Shoshone island becom- 

 ing enclosed in the stretch of land-locked wat- 

 ers east of the barrier, the Siskiyou island con- 

 tinuing in its marine environment. 



