burying beetle family, but it is a snail eater. It has a long head and a poisonous bite. Both adults and larvae eat snails.
I found it on a woodland path in late May. Unfortunately my dog had stood on it and killed it. I noticed it because it was so shiny. I imagine it had got washed out of a tree as we went for a walk after a heavy shower. Since then I've seen a few more in the moss around the base of tree trunks and on the trunks itself. I haven't seen one eating a snail yet though. Perhaps they bite them then bury them.