This species is an irregular, egg-shaped sea urchin. It is found from Alaska (Aleutian Islands) to southern California and the Gulf of California (Lambert and Austin 2007). Heart Urchins are deposit-feeding species that ingest mud. Lambert and Austin (2007) say: "Heart Urchins are deposit feeders, ingesting mud as they move through it. They live below the mud surface but maintain a chimney to the surface with large modified tube feet to obtain oxygen."