HO W EXTINCT MONSTERS ARE PRESER VED. 23 
to future explorers. Already, one remarkable and large horned 
quadruped has come from this region ; and it is known that other 
valuable treasures are sealed up within these hills, only awaiting 
the “ open sesame ” of some enterprising explorer to bring them 
to light. 
As previously pointed out, deposits formed in lakes are the 
most promising field for geologists in search of the remains of 
old terrestrial quadrupeds and reptiles ; but, unfortunately, such 
deposits are rare. 
It is very much to be regretted that the carelessness and in- 
difference of ignorant workmen in quarries, clay-pits, and railway 
cuttings have sometimes been the cause of valuable fossils being 
broken up, and so lost for ever. Unless they are accustomed to 
the visits of fossil-collectors who will pay them liberally for their 
finds, the men will not take the trouble to preserve any bones 
they may come across in the course of their work. (An example 
of this negligence will be found on p. 95.) But when 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 guardians 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 iron implement they carry with them. 
