Included in Red List No. 2, Non Marine Molluscs as extinct, albeit perhaps in this case its presence in Ireland in the first is debated:
Known in Ireland only from limestone bluffs in the gorge of the River Blackwater, Carricka-Brick Castle, Fermoy, East Cork (Phillips, 1914). Its status as a native is questionable according to Kerney (1972), who failed to find living material during a visit to the site in 1971. No live specimens have been found in recent times. It is known mostly from limestone rocks and quarries in Britain where it appears to be also declining.
This snail is, according to Wikipedia , a user of love darts when mating.
Séamus Sweeney 