van Straaten: No shingle. 



Steers: Isn't that true over on your east coast here (U. S. ) ? 



Zeigler: There is no shingle on the southern coast that I know of. There 



is shingle in parts of Massachusetts. 



Steers: That is the point I am always trying to make. You get the same 



principles going on but different conditions, perhaps due to dif- 

 ferences in shore, and you cannot make exact comparisons. 



Redfield: This is really a biological problem. Dr. Turner at Woods Hole 



has found that when small clams set along the lower part of the 

 beach and as they grow, the waves, presumably it is the waves, 

 tend to carry them up the beach presumably just as small and 

 large stones. 



van Straaten: Now that you mention this 1 may add an observation which I made 

 while studying the Rhone delta in southern France. There is a 

 small mollusc, called Corbulomya mediterranea, which lives in 

 great numbers in the barrier sands at depths between roughly 

 and 10 meters. While its shells are abundantly found on the 

 beaches, they were never encountered in water deeper than 

 about 10 meters, not even juvenile specimens with lengths of 

 as little as 1 millimeter. On the other hand, dead shells of 

 molluscs living in deeper water are rather commonly found in 

 the shallow zone of to 10 meters. It therefore seems tha.t, 

 in the Rhone delta area, there is hardly any seaward transport 

 of coarse material along the bottom in front of barrier coasts, 

 or at least no such transport passing the 10 meter depth contour. 



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