The T<wo Islands. 35 



Siskiyou island only changed to a Siskiyou 

 region, and the once Shoshone island to a 

 Shoshone region. And further, as the later 

 environment of the one was entirely marine, 

 and of the other entirely fresh water, it will 

 be most convenient to treat the ongrowth of 

 the Siskiyou island as including all west of 

 the Cascade barrier, and all the region east of 

 that barrier as the successive development of 

 the Shoshone, designating one as the Sho- 

 shone belt, the other as the Siskiyou belt. 



