SILURIAN FAUNA INTERPRETED EPICONTINENTALLV 793 
of this land was a pathway between England and eastern 
Canada. Other tongues reaching to the south were probably 
present through Asia and through the Pacific Ocean, the New 
Zealand communication coming through one of these. 
This interpretation of the Silurian, and similar interpretations 
of the other geologic periods, seem to call in question the gen- 
erally accepted theory of the exogenous growth of the North 
American continent, and seem rather to point to an endogenous 
process of growth. 
STUART WELLER. 
THE UNIVERSITY OF CHICAGO. 
