These Sea-urchins belong to the suborder Amphisternata of the Order Spatangoidea. The ambulacra on the upper side of the test is petaloid, widened and more or less sunk. The first plate of the posterior interambulacrum is developed into a prominent lip, partly covering the mouth and the transversely elongate peristome. Characteristic of this family is the ring of ciliated spines (the sub-anal fasciole) situated below the anus and eclosing a group of sanitary-drainbuilding tube-feet.
Four species of this family are found in the North Sea:
- Spatangus purpureus
- Echinocardium cordatum
- Echinocardium flavescens
- Brissopsis lyrifera