On the ventral side, the orifices are relatively small and the buccal membrane is closely packed with thick plates with many pedicellariae but no spines.

It occurs in a range of other habitats including under boulders and rocks, among seaweed, on rough ground such as oyster banks, in burrows in gravelly sediments and on the rhizomes of Zostera marina in seagrass meadows.

[3] Psammechinus miliaris is an omnivore and feeds on marine worms, hydroids, small crustaceans, molluscs, diatoms, macroalgae and detritus.

[6] Their grazing and predation have a considerable effect on the benthic ecology and if they are experimentally removed from an area, there is a significant change in the community of encrusting organisms.

Another study found that an individual urchin could eat 8 to 12 barnacles (Semibalanus balanoides) or 6 mussels (Mytilus edulis) in a day.

They are small in specimens caught in the wild but larger in individuals that have been eating prepared salmon food[3] and the possibility of aquaculture is being investigated.