Art,
According to the Treatise on Invertebrate Paleontology, Part 1, Mollusca
1, 1960, the species        Murchisonia (Hormotoma) gracilis (Hall) is
found from the Middle Ordovician from Quebec.  The group it is in was
given it's own suborder Murchisonina as it was not clearly anything else.
 Maybe you can see the mid whorl periphery with the slit and selenizone
(not unlike the modern Pleurotomariids).  There may be some more recent
work done on this, but it apparently dead-ended long ago.  Paleozoic
gastropods are facinating, but only locally common, so they get little
noticed except by a handfull of experts.

Allen Aigen (I did on a masters thesis on a Mississippian fauna)
Serirach.com

On Tue, 14 Nov 2000 21:34:40 -0500 Art Weil <[log in to unmask]> writes:
> Dear (probably Old Seashells and Andy);-
>         What I have here is a Hormotoma gracilis (maybe Homotoma?).
> It
> measures 13.48mm long and is about 400 million years old. Since a
> fleeting glance makes it look like an Epitonium (or Cerith or other
> coiled critter) I wondered if there is some descendency from the
> fossil
> that I have. Inquiring minds want to know.
>             Art