A vermetid gastropod, previously unreported from the Pacific Ocean, was found at O'ahu, Hawai'i, in aquariums at the Kewalo Marine Laboratory, in fouling communities on docks, and on intertidal and shallow subtidal coral rubble. It also occurs on coral rubble in Florida. Eggs, or nurse eggs, and early embryos are about 100 mm in diameter. Young are brooded in 1-13 stalked capsules attached inside the tubular shell. Intracapsular development involves an unusual complex adelphophagy (sibling cannibalism). Most eggs are nondeveloping nurse eggs. Ten to 20 eggs develop into apparently normal small veligers. Of these most arrest as small veligers, but a few grow to hatch as large pediveligers or juveniles. The species has a high potential for invasion and establishment following maritime transport or natural rafting. Protected intracapsular development ends with the release of crawling hatchlings that also produce mucous threads on which they can drift. Juveniles settle readily on hard substrata. An apparent rarity or absence of males suggests long-term sperm storage, hermaphroditism, or parthenogenesis, any of which could aid colonization. Adults and juveniles occur in fouling communities and can survive extended periods in still seawater and at low food levels. The species' global distribution and history of invasions are unknown. We predict widespread distribution and invasions in warm waters.