a dilemma. 



Barghoorn: I am well aware of that. I would like, if we have time, to devote 

 a few words to this. 



Russell: There is the matter of changing shells too. With us the Rangia 



cuneata is the brackish water clam; Unio the fresh water clam; 

 and the oyster a more saline indicator. In these mounds we 

 start out with one and wind up with another, even right through 

 the sequence, and do this in a short time. The artifacts may- 

 all be of the same cultural stage. 



121 



