This is a common mushroom around the karri forest and other places during the early part of the rainy season. It used to be listed as Macrolepiota konradii in guides until quite recently until Else Vellinga renamed the group in 2002. Almost all sources list this as edible, except for Tony Young who says that this Australian species is of unknown toxicity.
Its edibility seems to be based on the fact that is was thought to be the same as the edible M. konradii from Europe. Since this is now thrown into doubt, if not thrown out completely, I think it a wise precaution to avoid it. Besides which, I have a general aversion to Chlorophyllum and Macrolepiota due to the fact that they sometimes cause inexplicable gastric distress. I am sure that some people do eat or have eaten these though, so I list it here for completeness.
Here is a picture of the top surface.It is a rather pretty and delicate mushroom that will sometimes spring up in the oddest places. I had one come up once half way down a post hole that I had left open. The specimen pictured is about 150mm high with a cap 100mm across. That is a typical size. They don’t occur as a small mushroom. In fact, there are some small Lepiootas that look rather similar and some Lepiotas are deadly.
So I will abstain for the moment.
Update: August 2016
My fellow blogger Jsun and I picked some of these during July and he was able to confirm that they were the same as those he had eaten in the east. I watched him cook and eat some and being thus encouraged I had a small portion myself. I am now much more confident about these. One thing he pointed out to me was the ‘snakeskin’ pattern on the stem which also flares out at the base.
The ring or annulus is quite distinctive also, breaking up in radial splits and being attached at first, but moveable with some encouragement.