Top Shells - Family Trochidae

The Trochid family is very large and includes several subfamilies, many genera and hundreds of species, quite a few which are intertidal. The Trochid family includes the Top Shells, Kelp shells and Periwinkles.

The shells of Top Shells are cone-shaped, sometimes turban-shaped or pyramidal, or lens-shaped or oval-shaped. They all have an inner, thick, glossy to iridescence, nacreous layer inside the shell opening.

They have a simple outer lip. The calcareous operculum is round, with a spiral pattern and composed of horny material.

Top Shells are herbivorous, and are usually gregarious. Many prefer to live in algae or algae-covered rocks in shallow water.

Trochids have separate sexes and most species expel sperm and eggs into the water for external fertilisation. In some other species the female lays a gelatinous egg-mass, within which occur the early stages of larval development.

Some examples of Top Shells are:

Zebra Top Shell, Austrocochlea porcata. The common black-and-white stripped globe-shaped shell found at mid-tide levels around south-eastern and southern Australia.

Ribbed Top Shell, Austrocochlea constricta, the common buff-coloured and ridged shell found at mid-tide levels of southern Australia.

Wavy Top Shell, Austrocochlea concamerata, with its flatter shell, more numerous ribs and yellow-spotted or streaked interior. It prefers to hide in cracks and gutters.

References:

Bennett, I. (1987) W. J. Dakin's classic study: Australian Seashores. p,274, Angus & Robertson, Sydney.

Davey, K. (1998) A Photographic Guide to Seashore Life of Australia. p.87, New Holland, Sydney.

Edgar, G. J. (1997) Australian Marine Life: the plants and animals of temperate waters. p.237, 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. p. 38, Museum of Victoria, Melbourne.

Macpherson, J. H. & Gabriel, C. J. (1962) Marine Molluscs of Victoria. p.69, Melbourne University Press & The National Museum of Victoria.

Shepherd, S. A. & Thomas, I. M. (1982) Marine Invertebrates of Victoria, Pt. 2. p. 551, South Australian Government Printer, Adelaide.

Underwood, A. J. & Chapman, M. G. (1993) Seashores: a beachcomber's guide. p.30, New South Wales University Press, Sydney.

Wilson, B. R. & Gillett, K. (1979) A field guide to Australian Shells: Prosobranch Gastropods. p. 35, A. H. & A. W. Reed, Sydney.

Molluscs
Top Shells & Relatives

Zebra Top Shell
Ribbed Top Shell
Wavy Top Shell

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