Hi again,
You are right about that - I've had it happen - I recently received 4
"argyrostomus" and there were 3 different opercs!   But in this case, I
purchased T.margaritaceus more than 20 years ago, and I recently received an
un-named Turbo, also from Thailand, that was identical and the operc was also
identical to the first margaritaceus.
Also, the more books you check, the more confused you can become - errors you
don't find out about until years later, or pictures in one book that look
nothing like pictures in another book.  Thanks once again.  Carol Brunner