Regarding the unidentified shell that has defied definite I.D., I agree with
Paul Monfils who wrote that it seems to be a distorted Ancilla.  Perhaps a
new species which is also a Freak, in which case, no one will be able to
identify it positively.  If it is also from the
Patagonian Region, the case for Ancilla is stronger.  It would be interesting
to see what the Curators of Shells in Museums with major collections would
say.    Wil