A relatively common Agaricus species in the Southern Dandenongs is this white to grey-capped firm Agaricus species that sometimes smells like kelp or seaweed – a species that BLASTn places at 100% numerous Agaricus bernardii sequences.
I often find it under various conifers. It readily stains pink to red when sliced which differentiates it from the less common and way tastier Agaricus bitorquis.
Ive never tasted it because the smell puts me off.