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  Plate 
  23.— 
  Aerial 
  photos, 
  vicinity 
  of 
  Pisco, 
  Peru. 
  Top: 
  Strange 
  belt 
  of 
  pock- 
  

   markings 
  on 
  ridge. 
  Bottom: 
  Ancient 
  irrigation 
  system 
  in 
  Pisco 
  Valley, 
  cultural 
  

   affiliation 
  unknown. 
  (Courtesy 
  James 
  Sawders.) 
  

  

  