Photo 1:  Mopalia ciliata. 


Hairy Chiton specimen found at Cattle Point Beach, San Juan Island, WA. 


Photo:  Dr. Bonnie Becker



Chitons are a small class of marine molluscs characterized by 8 overlapping dorsal shell plates or valves that are held by a leathery girdle.  In some species though, the valves have become reduced and can appear to be embedded in the fleshy girdle.  Their body shape exhibits bilateral symmetry (Levinton 2001, Kozloff 1993).


Chitons cannot withdraw into their shells, but rather clamp down and adhere to the substrate via suction with their powerful, flattened foot.  This protects them from both predation and wave action (Levinton 2001, Kozloff 1993).


Their preferred habitat is a rocky substrate that extends from exposed rocky beaches and shallow tidal pools up to 365 feet (110 meters).  Most species prefer rocky low intertidal to subtidal zones (Levinton 2001, Kozloff 1993).


Most chitons are grazing herbivores, feeding on encrusting algae.  A few species from the genus Mopalia also eat diatoms, sponges, hydroids and bryozoans (Kozloff 1993). 


Basic Chiton Taxonomy

Kingdom:  Animalia

Phylum:  Mollusca

Class:  Polyplacophora

Order:  Neoloricata

             Suborders:      Acanthochitonina





Genuses represented in Washington State include:  Tonicella, Mopalia, Cryptochiton, Katharina, Placiphorella, Dendrochiton, Lepidochiton, and Lepidozona


(ITIS 2007, Kozloff 1993, Sept 1999)

Photo 2:  Katharina tunicata. 


Black Katy Chiton specimen found at Cattle Point Beach, San Juan Island, WA.


Photo:  Lisa Hannon