Okay, many thanks to Kurt and Helmut!!  I knew we had the expertise on tap.
I will go back and let the man know what snail he has in his cattle tank.
Yet another introduction from across the big pond.  We even have the Asian
clam in the state (Corbicula fluminea).  When I left to join the Air Force
in 1969 they were not here.  By the time I came back in 1994 they were
everywhere.  No competition and not many predators, although I'll bet the
coati mundi and ringtail cat eventually figure out how to eat these
delicacies.

Thanks again,

Tom