Coprinellus disseminatus, or Coprinus disseminatus, is from family Coprinaceae. Typically, fungi from this group have black gills that quickly dissolve or self-digest into an inky black gooey substance (the official mycology term is "deliquesce"), but Coprinus disseminatus does not collapse and auto-digest. This is a useful feature for identification purposes.
Stipes (stems) are white, hollow, smooth, and fragile, growing to about 35mm high and only 1 or 2mm in diameter. Gills start out white, aging to light brown then dark brown or blackish-brown. Unlike other Coprinus species that auto-digest, it should be possible to obtain a spore print from Coprinellus disseminatus. Spores are black or blackish-brown.
Coprinus disseminatus are fragile, crumbling when handled
Coprinellus disseminatus grow on decaying wood and often appear on wooden garden edges or stepping blocks. They also sprout from underground decaying roots. I have also seen them growing amongst wood-chip mulch. They will appear in large troops, primarily in autumn and spring.
Coprinellus disseminatus are not restricted to Australia, but I am unsure of their distribution in Australia.
A fresh specimen with hollow stalk
Although not Australian, here is a Coprinus key that could be a useful aid in identifying Coprinus species found in the field. And here is an earlier blog entry detailing another Coprinus species, Coprinus cinereus.
Aging specimens dry out and wither, but do not collapse by auto-digestion like most other Coprinus species