The inkcap group of mushroom species get their name from their caps which deliquesce as they have shed their spores. From the rim inwards they turn into a black mushy-looking mass which then disappears. The deliquescing black mass from one of the larger and more common inkcap species was the main ingredient in one recipe for making ink in centuries gone by.
This is the last remant of a magpie inkcap with deliquescence almost complete, and another in a similar state peeping out behind.