Two-Toothed Door Snail

I love this photo. I was looking at the lichens and bryophytes at about head height on a mature oak on the Downs a couple of weeks ago. Imagine my surprise when I saw this sticking out of a hole in the lichen. 
 

Initially I thought someone must have put it there, but removing it soon revealed it was alive and well.
It's the first land mollusc on the blog and nice to have such a groovy one: the two-toothed door snail or Clausilia bidentata. I don't think I've seen one before but they're fairly common, found throughout the British Isles, usually in woodland. They are most active at night or when it's wet. It had rained heavily before my walk and this encourages them to climb trees to graze on lichens and algae.
Molluscs are the second largest phylum in the animal kingdom after arthropods. However there are 85,000 described species compared with 1.2 - 10 million arthropods. Snails are in the class Gastropoda and the family Clausiliidae.