MAP SHOWING APrALACITIAN TROUGHS 



293 



this proposition, the chief aim of my stratigraphic and paleontologic in- 

 vestigations in the past decade has been the location of such lines of pre- 

 dominating upward movement. The determination of these lines is 



H- ^ 



deemed one of the best results of a long series of personal field studies 

 and comparisons of faunas gathered with a view to illustrate minute 

 details of stratigraphy as well as their geographic distribution and varia- 

 tion. Moreover, the plotting of these lines has been an essential factor 



