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.
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.
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