DIASTROPHISM AND THE FORMATIVE PROCESSES 425 
distinctly localized phenomenon occurring where the compressive 
stresses exceed the strength of materials. 
In conclusion, it is felt that the shell-deformation is intimately 
related to the less obtrusive diastrophism of the subshell mass. 
The plunging zones that form the common border of the interlock- 
ing tracts give suggestive intimations that may have wider applica- 
tion and more profound significance. These form a line of 
approach to the larger diastrophic problem and so properly con- 
stitute a part of the groundwork for the study of megadiastrophism. 
