This is an immature stinkhorn. The outer skin has been chewed away to expose the jelly-like wrapping around the immature fruitbody. At this stage I can't tell for sure what species this is, though I suspect it's an Ileodictyon. Nevertheless I think the photo is educationally useful and I'd planned to create a miscellaneous stinkhorn 'species' for it but find I can't add new species in the stinkhorns. Presumably a temporary glitch, so I'll have another go later.