Confidence: I'm as sure as I can be.
Notes: This refers to the photo on the left. The breathing pore is towards the front of the mantle, and the back end of the body is 'rounded' and covered with very large tuberles. So large in fact that I wonder if it is am immature Arion flagellus? However, the photo on the right does look like Boettgerilla - translucent purple grey with keel towards tail.