Re: New Jersey snails: Lunged snails such as pond, bladder, and ramshorn snails and limpets are hermaphroditic. Some of these can self-fertilize, some can't. Gilled snails such as periwinkles, nerites, and live-bearing snails have separate sexes and cannot self-fertilize. Gilled snails can be identified by the presence of a "trap-door" or operculum.