double linked glists

["BIRCH, JANET M" <JBIRCH entergy com>]

  is the correct behavior of these lists to stop traversing when they reach
their limit ?
 I mean if I'm going forward through my list and I reach my last entry, I
should then be able to 
prev back to the front, right ?    well, mine aren't doing that.  they stop
going any direction.  

am I doing something wrong, or I am I just expecting a behavior that isn't
there ?