Eight West African countries agreed this week to replace $1 billion worth of paper currency with new bills. The countries that use the franc of the African Financial Communityknown by its French acronym, CFAas their common currency have seen a wave of bank robberies and counterfeitings in the past few years. The new money will have metallic strips to deter counterfeiters, and will feature designs of African art and animals. The changeover will also have a fringe benefit: cleanliness. CFA countries havent put fresh bills into circulation for more than 10 years, and many of the francs are so dirty theyre slimy.