Garlic Anyone?

I thought that a large leaf had fallen from one of the trees in the garden. It wasn't a leaf; it was moving. the shell alone was more than 10cm long, with the entire snail at about 12-14 cms. Massive. I like the shape of the shell, because it is unlike any normal land snail, as it looks more like a water-living creature. Trouble is that Mali is land-locked and very dry for most of the year. As soon as the rain appears, these must make the most of it, then hide in a sheltered spot for 9 months of the year.