Many thanks to Andrew McCutcheon for sending notes and pics of a Shovelnose Lobster Ibacus peronii (also known as Balmain Bug) found on its back on the beach at the Spit Nature Conservation Reserve on May 20/09. The critter was alive (but not at all lively) and released back to the water.
The Museum Vic website says Balmain Bugs grow to 230 mm long and live on soft sand and mud at depths between 10 and 250 m. They’re distributed across southern Australia from southern Queensland to central Western Australia.
Edgar’s ‘Australian Marine Life’ says that like their relative, the Wollongong Bug, they live in deeper waters in coastal bays on a soft silt bottom, are moderately common, and excellent eating but not as popular as rock lobster. The animal’s flat shape enables it to partly bury in exposed, soft sediments.

shovelnose underworld (pic by Andrew McCutcheon)
The species is mentioned on the Fishnet website (dated May 1, 2006) fishnet.com.au as follows:
Jack asks:Geoff, While fishing off Clifton Springs I caught this creature, reddish in colour, that looked to be a cross between a crayfish and a crab. Do you know what it would be?
Geoff says: Jack, the creature you caught was almost certainly a shovelnose lobster or Balmain Bug (Ibacus peronii). They used to be fairly common in Port Phillip Bay prior to scallop dredging. Perhaps they are making a comeback.
Maybe they are. But finding a ‘deeper water’ species almost on the beach raises some doubts, at least for this animal. But hey….. maybe the freckled colouring indicates a whole new species, the Werribee Bug, Ibacus mccutheoni ? 🙂