Someone opened this shell up in order to make it display as a heart shape.

You can see how, in this species of Atrina, the adductor muscle scar (greyish) bulges up out of the nacreous (blue and green pearly) area of the shell.

However, if you look carefully in the otherwise very similar species Atrina seminuda, in adult shells you will be able to see that the adductor muscle scar is contained entirely within the nacreous area.

In live or very freshly dead individuals, the visible soft parts of Atrina rigida are grayish or bluish, whereas the sort parts of Atrina seminuda are orange.