I saw this slug while birding the Bulb with Sarah a few weeks ago, except it was raining and I didn't have a camera. This time I went out just for the slug. Found it in exactly the same place... and then found a billion more. I must have seen at least 100 in the enclosed pond at the end of the Bulb. Madness.Still haven't made up my mind about the species. Looks a lot like the pics of both H. japonica and H. vesicula.Update: upon consulting some more photos and noting the orange dots on periostracum (the membrane surround the shell), I'm pretty sure this is Haminoea vesicula.Update 2: dieta pointed out that the head shield is bifurcate, which means this is Haminoea japonica.