Ross:
 
In Cypraea there are several groups of species that are not possible for
people I know to separate:  The C. rashleighana group eg C. burgessi
differ from others only by mantle characteristics and/or radulae.  In
the C. carneola group two differ by mantle papillae and by a ring around
the shell which fades quickly and isn't present on all shells so they
can't be separated unless fresh shells are involved.  In Bursidae, I
found two species that have different opercula, which would make them
different species.
 
Aloha,
 
Wes