Turbulent of water
A thick and heavy shell- provide extra stability
strong ribbed valves- to strengthen against wave action
a large pedicle opening- to support large pedicle to secure attachment
a folded margin- to reduce sediment getting into mouth
adaptions in quiet water
no pedicle opening- peddicle not needed
week ribbed valves or smooth- quiet conditions
may have median fold or sulcus- to seperate curents of water entering and leaving the animal
may have extension of valves to form 'wings'- to provide large surface area to prevent sinking into the sediment
adaptions in a sof muddy substrate
valves flat with large resting area- to provide a large surface area to prevent sinking into sediment
one margin of the shell may be turned upwards, away from the sediment- to ensure that some part of the shell remain out of the sediment for feeding
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