One additional thought, within the context of what I said before - there probably is a reason why the smallest protoconchs are not found in land snails. Among marine snails, the smallest protoconchs (and sharpest apices) are generally found among those species which have a free-swimming veliger (embryonic) stage in their life cycle. Species which give birth to fully formed, shelled young, or in which shelled young emerge from an egg capsule, usually have a larger protoconch. Since land snails do not have a veliger stage, their minimum protoconch size is likely to be larger than that of aquatic species. Paul M.