434 THE CAMBRIAN. [bull. 81. 



Topographic features in correlation. — Topographic features may indi- 

 cate relative geologic age in the discussion of the later formations ; but 

 in dealing with the Lower Paleozoic it has thus far been found to be 

 impossible to obtain the evidence of newer or older topographic features 

 that are of value. Mr. Gr. K. Gilbert has used it successfully in discuss- 

 iug the age of the Equus fauna of Lakes Mono and Lahonton of Cali- 

 fornia and Nevada. 1 



1 U. S. (ieol. Survey, Monograph, vol. 1, 1890, pp. 393-402. 



