Explanatory Note 



The Special Scientific Report series comprises 

 results of investigations, usually of restricted scope, 

 intended to aid or direct management or utilization 

 practices and as guides for administrative or legisla- 

 tive action. Reports in this series are issued in 

 limited quantities for the official use of Federal, 

 State, or othex' cooperating agencies, and in processed 

 form for economy and to avoid delay in publication. 



