Found these the other day while turning over some logs in a forestry...
They where on what looks to be a silken web covering over fungus growths. Size varied from about 3/4 inch to 1 inch approx. They moved around by contracting waves up they body.
I have seen another image like this on the web, i belive it is on whats this bug?. Here it is still a mystery, and i believe somone thinks it is a slug