Helmut,
 
I also agree.  I have one of the "cheap" Cypraea fultoni and when you
have the actual shells to look at they are totally different.  Cypraea
mus and Cypraea teulerei are somewhat similar but Cypraea fultoni isn't
even close to these two.  And none of them look like Cypraea stercoraria
to me.  However they are all more like each other than they are like
most other Cypraea (which is what I think the original gist was).  I
don't know enough about cowries to know if this means anything.  Have
they ever been grouped into the same subgenus?
 
In any case, they are not bad looking.
 
Tom Eichhorst in New Mexico, USA