Heart urchins are burrowing echinoids. This life-style is similar to that of sand dollars, but the heart urchins belong to another group. Heart urchins belong to the Family Loveniidae in the Order Spatangoida.
Echinocardium is the standard British heart urchin on sandy shores. Its spicules are converted to soft form, and they have sticky tube-feet which pass food to their gut. They can burrow up to five times their own height, and still keep connection with the surface for oxygenated water and food.