Thanks Gert!
 
How interesting!  Apparently Lamarck proposed Nassa as a new genus
for the species Linnaeus had named Buccinum mutabile (which we now
know as Nassarius mutabilis), in 1799.  However, the Muricid genus
Nassa, named by Roding, dates from 1798, just a year earlier!  I
would guess (but will wait to hear from the pros) that this is why
the Muricid genus Nassa is valid, but the Nassariid genus Nassa has
been replaced by Nassarius.  This raises yet another mini-question.
Is the author's name spelled Roding, or Roeding?  I see it both ways.
 
Paul M.