The False Limpets belong to the family Fissurellidae. They are distinguished by having the shell marked in some way. This is a product of the mantle having a slit in its margin.
Black Keyhole Limpet,
Most False Limpets, as their name suggests, have shells which look very similar to the limpets. However, if you look closely most have a notch in their shell on the outside margin. They are called slit-limpets. Another group have a hole at the shell apex. They are called keyhole-limpets.
Elephant Snail, Scutus antipodes.
Another member of this group is the aberrant black Elephant Snail, which looks nothing like the other members of the group. The soft parts of this animal are jet black, while the shell is white. At the front of the shell is a shallow fissurellid notch, showing that it belongs to this family.
Bennett, I. (1987) W.J. Dakin's classic study: Australian Seashores. Angus & Robertson, Sydney.
Davey, K. (1998) A Photographic Guide to Seashore Life of Australia. New Holland, Sydney.
Edgar, G.J. (1997) Australian Marine Life: the plants and animals of temperate waters. Reed Books, Kew.
Quinn, G.P., Wescott, G.C. & Synnot, R.N. (1992) Life on the Rocky Shores of South-Eastern Australia: an illustrated field guide. Victorian National Parks Association, Melbourne.
Marine Research Group of Victoria (1984) Coastal Invertebrates of Victoria: an atlas of selected species. Museum of Victoria, Melbourne.
Macpherson, J.H. & Gabriel, C.J. (1962) Marine Molluscs of Victoria. Melbourne University Press & The National Museum of Victoria.
Shepherd, S.A. & Thomas, I.M. (1982) Marine Invertebrates of Victoria, Pt. 1. South Australian Government Printer, Adelaide.
Underwood, A.J. & Chapman, M.G. (1993) Seashores: a beachcomber's guide. New South Wales University Press, Sydney.
Wilson, B.R. & Gillett, K. (1979) A field guide to Australian Shells: Prosobranch Gastropods. A.H. & A.W. Reed, Sydney.