Cortina...

....in some mushrooms with gills, a veil-like membrane extending downward from the outer edge of the cap.

One of the largest genera of fungi, Cortinarius (often known as webcaps), is characterised by the presence of a cortina, though this web-like veil also occurs occasionally outside this genus. 

This little fungus, a couple of centimetres across the cap, has popped up on our lawn in the last couple of days, and may well be a Cortinarius. I'm taking a spore print tonight, but I doubt if I'll ever be able to put a name on it - apart from the delicate cortina, it's rather featureless and Cortinarius are very difficult to identify!

Another report finished today - five more to go, though sadly these include the two really large ones!