Help identifying these little guys...

[paul monfils]

HA HA  Is my face red!  Never thought I would get fooled by one my commonest local shells :-)  It's a matter of scale.  When I looked at your picture the first time I figured the bivalve was maybe 3 inches or so and the snails were maybe a half inch.  They kind of resembled immature Cerithium, but not really - which is why I asked about the locality.  Now that you tell me the location - a location where I myself have collected a number of times - I realize that both the bivalve and the snails are much smaller than I had estimated.  These are Bittium alternatum.  I believe it is the most abundant gastropod on the south shore of Cape Cod.  I have shaken a handful of seaweed in a bucket of water and come up with more than a thousand of them.  I'm in Providence.  I have collected in Fairhaven-Mattapoisett-Marion-Wareham many times.