One of the interesting finds during last month's trip to Florida was this Batillaria minima with a funky shell. Well, I think it's a Batillaria minima; I found it among Batillaria minima and the microsculpture of its shell, its operculum and the morphology of its head look like those of Batillaria minima. But if you think it may be a different species, let me know.
Here is what a normal Batillaria minima looks like.
What may have caused this snail's shell to resemble a screw? I don't know. There are no injury scars on it and because the screwiness starts near the apex, I suspect the cause was internal. Perhaps a parasitic infection? Batillaria are known to carry trematodes.
I have the snail here, by the way, and it's still alive.