Distribution: Tropical Western Pacific and Indian Oceans, Hawaii, Western Atlantic and Caribbean; shallow water; burrowing in coral rubble or soft rock; common. Natural History Notes: The only sipunculan with documented asexual reproduction. Characteristics: The genus is characterized by a dorsal anal shield which is round, notably dark, and in this species inparticular, without grooves. Body wall musculature not in bands. Posterior end sometimes forms buds.