They belong to a species of Venonia Thorell, 1894, one of the few web-building wolf spiders (Lycosidae). Most species of wolf spider hunt their prey, but Venonia sits in a burrow at the centre of the web and waits for an insect to approach. Then the spider darts out and drags the unfortunate creature back to the burrow.
Most of these spiders are timid and retreat when a camera looms over them, but this one held its ground long enough for me to take several photos, all of them not quite in focus. This is the least fuzzy. I'll have to give it another go.
I'm not sure which Venonia this is — species are differentiated by reproductive anatomy — but the sheet-web wolf spider V. micarioides (Koch, 1877) is by far the most widespread and common species in Australia. In suitable habitat, their webs cover the ground by the hundreds. I suspect the ruthless grazing here keeps the numbers down.
Further reading
Yoo, S-J. & Framenau, V.W. (2006) Systematics and biogeography of the sheet-web building wolf spider genus Venonia (Araneae: Lycosidae). Invertebrate Systematics 20: 675 – 712.
