Volvopluteus gloiocephalus (Big Sheath Mushroom)

The fruit body is a mushroom that grows on the ground. The caps are conical early on and flatten with age but retain a noticeable central bump. The caps are greyish to grey-brown, smooth, sticky in moist conditions and up to 15 centimetres in diameter. The stems are smooth, of a similar colour to that of the cap and often 10-15 centimetres long.  In the immature stage there is a universal veil, i.e. a membrane that envelops the entire button stage of the mushroom. As the stem extends, that veil is broken but a remnant is left as a cup-like surround (or volva) at the base of the stem. This may be obscured by grass, mulch, etc and you may need to (carefully!) pull aside grass, mulch etc to reveal it. You see an example in this photo: http://www.cpbr.gov.au/fungi/images-captions/volvariella-speciosa-0309.html. Very, very few mushroom genera have volvas, so the presence of a volva is very helpful when it comes to identification.

The gills are pale pinkish at maturity and the gills are free, i.e. no gill is attached to the stem. If you look at the underside of a mushroom cap you typically see gills of a variety of lengths (e.g. http://www.cpbr.gov.au/fungi/images-captions/marasmius-elegans-0032.html) extending in from the margin. In almost all genera, the longest gills extend from the margin to the stem, but in the few genera even the long gills fall short of the margin. This leaves an empty,  circular channel around the top of the stem (as here for example: http://www.cpbr.gov.au/fungi/images-captions/agaricus-sp-0037.html).

The spore print is flesh pink or pinkish brown. There are few genera with a pinkish tint to the spore print.

Volvopluteus gloiocephalus was once considered to belong to the genus Volvariella, and you may see references to it as Volvariella speciosa, Volvariella speciosa var. gloiocephala or Volvariella gloiocephala.