Phil, Harry, et al:

I'm rather anticipating that the answer to the following question is yes
- I'm not suggesting any lack of conchological erudition - I know better
- but just to cover the bases - are you sure you are looking in the
right place?  I grew up collecting shells in New England, yet until a
few years ago I had never found a live specimen of the common Melampus
bidentatus.  Then, one sweltering summer day I found some - HUNDREDS of
them - miles from where I would have expected to find any seashells.
But of course, they are not "seashells", that's the point.  I found them
in a brackish headwater of a river, about 3 miles above the mouth.  They
were under stones and dead, matted grass, in an area which might have
been dampened a couple of times a day, at extreme high tide.  They were
50 or 60 feet above the water's edge at low tide, which is when I was
there.  There was not another shell of any kind in sight, not a
Littorina, not even a Geukensia demissa, which love muddy, brackish
water situations.  Such species could be found farther downstream, but
this location was apparently to "fresh" for them.  If Tralia is similar
in habit, maybe they could be found in such an area.  What I remember
most about the outing though, is that my daughter and I emerged from the
grass and brush covered with ticks.  Ugh!  We drove to a nearby
restaurant, went to respective restrooms, and shook out everything.  But
at least I finally got some Melampus.

Regards,
Paul M.