At 01:15 PM 10/11/01 -0400, you wrote:
>Not to belabor the point, but breaking off pieces around the aperture of the
>shell would actually reduce, not enlarge, both the size of the aperture, and
>the size of the overall shell, including the available living space within.

Breaking the outer lip makes room for the large claw which grows to fill
the opening and more. Have I not read of crab predation on shelled mollusks
leading to evolution of  heavier shells?

As long as we're on the subject, I've always wondered why hermit crabs
congregate by the hundreds under just one or a few rocks at extreme low
tide. It makes for marvelous collecting of deeper water stuff without
getting wet. But hundreds of similar rocks don't have such concentrations.

John