The Echinodermata are generally large, benthic invertebrates such as the sea star, sea urchins, sand dollars and sea cucumbers. Sea stars and brittle stars can be found on sandy or sandy-mud bottoms from the surf zone to deep water. Brittle stars are also found on oyster reefs. Commonly found on jetties, sea urchins may also live on sandy bottoms. Beds of sand dollars may be found in sandy sediments just beyond the surf zone or in the passes. Sea cucumbers are usually found on grass flats.