This has started to dry out, hence the wavy gills. In Agaricus the mature spores are brown (commonly a dark chocolate brown) and so give the gills that colour. Here the spores are presumably a pale colour and certainly Lepiota/Macrolepiota and their kin have white spores. In those genera you usually see concentric rings of scales on the cap, the scales more densely packed the closer you get to the centre. I'm not convinced that that is the case here - but with the cap having started to dry it's harder to be sure. Often those scales are of a different colour to the underlying flesh, so that you actually have a patch of solid colour in the middle. In both Agaricus and the Lepiota group there is a membrane that covers the gills before the cap expands. On expansion that membrane remains as a ring or skirt of tissue around the stem. I don't see any traces of this, but in some species it can be easily damaged.