Hi James,
I believe Norrisia norrisi Sowerby is the only living member of the genus.
On an old listing of fossil species I have, I see a Norrisia microphalus
listed, from the Eocene deposits of the Gosport Formation in Alabama. I know
nothing about it.
Norrisia has a really neat operculum. It looks like a coil of rope.
Regards,
Paul M.