This is Lymnaea stagnalis or the giant pond snail. It's pretty common but has been important in allowing us to develop an understanding of how neural networks work. They have a very simple nervous system of around 20 000 neurons which are all quite large. Consequently they have been the subjects of many experiments. This may explain why this one defaecated on me when I picked it up.
They are molluscs and belong to the gastropod class. They are hermaphrodite and demonstrate the Coolidge effect, something the chaps out there might know something about (nudge, nudge, wink, wink).