The valves of the shell are roughly circular and the upper one is decorated with many spiny protuberances up to 5 centimetres (2.0 in) long.

[4] The color varies but is usually white or cream with orange or purplish areas making it well camouflaged to hide from its predators.

[5] A diver swimming past may just observe a slight movement on the seabed as the oyster snaps its valves shut.

It is also a member of the fouling community, being found on sea walls, man made structures and wrecks.

[6][7] The Atlantic thorny oyster is a filter feeder sifting out plankton and other organic material from the water that passes over its gills.