Thanks to Bill Frank and Paul Mofil{s. I have all but one of the worlds Tonna
in a case with a glass front so it is easy for me to match up the shells. I
think tetracotula is the only one I do not have this one is not tetracotula .
 It has 20 very shallow,evenly spaced ribs ,light tan outside,dark tan inside
,almost brown. To me this is the fun part of collecting when you get down to
the end of a family or think you are at the end and find one more.THANKS
AGAIN.GLENN TOLMAN HOUSTON TEXAS USA    ( It is Far away from any in the case
)