We have to take every sample of soil, let it dry and than use water to separate stones, soil and snail shells. As the majority of shells is smaller than 3 mm, it was really hard work. Separation of 1 sample took more than 7 hours of work. And then we have to determinate each and every species of snail.
We found in total more than 3500 snail shells, so the determination was really exhausting and time consuming.