Well, Maurizio, it depends on which one you think you are.
 
It is generally thought that a Conchologist studies the physical
aspects of molluscan shells while the Malacologist is concerned
with the physiolgy of the molluscan animal.
 
And while there are some mollusks without shells, there are no shells
without mollusks. (Non sequitur -- but sounds nice!)
 
That's my take on the two. There are others.
 
 
Aloha,
 
makuabob (a.k.a. Bob Dayle)