26 EXTINCT MONSTERS 
once they realise that such finds have what political economists 
call an “exchange value,” or, in other words, can be turned into 
money, it is astonishing what zealous guardiaus of Nature’s 
treasures they become! For this reason collectors often find 
what Professor Bonney calls the “silver hammer ”—in other 
words, cash—more effective than the steel implement they carry 
with them. 
