Chitons, Amphineura and Polyplacophora


Ischnochiton australis, various sizes, under rock, Long Reef, Sydney, NSW, Australia. 21 December 1995. Photo: Bill Rudman

Chitons are a small class of marine molluscs, characterised by their possession of 8 dorsal shell plates usually held in place by a leathery girdle. They are bilaterally symmetrical and are usually found on hard intertidal or shallow water surfaces. In some groups however, the shell plates become reduced in size, and are often embedded in the girdle which becomes more fleshy and in some cases brightly coloured. Chitons are grazing herbivores, found in all parts of the world. They range in size from the huge Californian Cryptochiton stelleri, which grows to 300mm in length, to some that never grow more than a few millimeters in length.

I have included a page on chitons in the Forum,, because as the message below, illustrates, some chitons do look surprisingly slug-like.

Authorship details
Rudman, W.B., 2002 (November 24) Chitons, Amphineura and Polyplacophora. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

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