Arion subfuscus is common and may be found when conditions are wet and, especially, in the early morning. Slugs are snails. Like other gastropod molluscs they have a shell but theirs is carried internally and has been reduced to just a sliver. Like other land snails, Arion has a pneumostome which allows air to reach the lung. In this image you can see a hint of this feature if you look a third the way down the right side of the mantle (the oval structure which leads from the base of the optic tentacles). I think this is a very pretty animal indeed.