Just for added frustration......all forms of Polygyra septemvolva Say, 1818
and Polygyra cereolus (Muhlfeld, 1816) are bull.....None of characters used
to differentiate these hold up even within a single population.  There are
two species of Polygyra (s.s.) in Florida, perhaps three, if P. bahamensis
is actually introduced there...  They are septemvolva and cereolus.
The only character that really works is the shape of the umbilicus.
Cereolus is tubular (straight-sided), septemvolva is funicular
(funnel-shaped, widest at the base of the shell).
Cereolus occurs in Florida, throughout the coastal regions of the southern
part of the state to Key West, it vanishes along the west coast from about
Pasco to Franklin counties and then picks up again.  It occurs sporadically
along the coast all the way around to Campeche, Mexico.  On the east coast
it goes as far north as South Carolina (maybe just Georgia, I forgot).
Septemvolva occurs in the interior part of the state, replaces cereolus in
western central Florida and then poops out in the panhandle.
Anyway, here's the rub.  Museum collections indicate that cereolus started
popping up all over in Florida after 1950.  Interior metropolitan areas,
roadsides, even inland counties in other southeastern states.  This great
range expansion corresponds with the big land development booms of Florida.
 They are transported in plant pots and sod for people's yards and along
roadsides.  But some of these are reported to be P. bahamensis.  I haven't
put my mind at rest about that yet.  This may be, maybe not.

Eike Neubert published a paper a few years ago on an occurrence of this
pesky little thing in Saudi Arabia.

All other "Polygyra" in Florida listed by others are assignable to other
genera.  Ken Emberton got most of that straight before he went off to
Madagascar.  For instance, Polgyra auriculata is now Daedalochila
auriculata, etc.

Polygyra (s.s.) is lenticular, multi-tight whorls, small round aperture
with only one tooth, the one in the parietal area.  Daedalochila,
Lobosculum, etc. have more apertural barriers, but the real differences are
in the soft anatomy.

Back to working on the Appalchicola "lagoon".

Kurt