No. 521] FACTS ABOUT THE " LOBSTER PEARL " 301 



growth (marked a) may be represented here as extended 

 too far below the surface. The relations, however, are 

 the same, whether this pocket is deep or shallow, and no 

 attempt is made to express any possible mechanical 

 conditions which might determine the inward rather 

 than outward direction of such a fold. 



