The Ophiocoma erinaceus has disc scales that are encrusted with rounded granules, and these granules extend into a V-shaped area between the arms on the underside of the central disc. The body is uniformly black and some individuals have white markings along the lower arm plates. Their tube feet are a vibrant orange color. The upper arm plates are wider than they are long with one side being narrower. The arms are equipped with long, robust spines that gradually become shorter towards the tips.