Model of a Chiton

Chitons are marine mollusks in the Class Polyplacophora.  They live in the intertidal and subtidal zones.  They all have eight armored plates on their dorsal side for protection from predators.  They can roll up into a ball when disturbed, like pill bugs do.  Their armored plates are surrounded by a soft girdle.  They have a muscular foot that they use for locomtion.

Chitons have gills for respiration which are located on their ventral side, underneath the mantle (a layer of tissue between the shell and the visceral mass), and surrounding the foot.  They have a mouth, which contains the radula, a raspy organ that they use to scrape the algae that they eat off of rocks.  They also have an anus.  They have a heart and an aorta.  Their nervous system includes a nerve ring that surrounds the mouth.  They have  primitive eyes that are part of their shell and see only pixellated images.

They are dioecious, i.e., individuals are either male or female.  The chiton's trochophore larvae  are lecithotrophic, which means "feeding on yolk". They do not go through a veliger larval stage.  Instead, they feed on their egg yolk,  growing bigger over time. They eventually fully absorb the yolk, and become adults.

One medium sized tropical species, Acanthopleura granulata, commonly known as the West Indian Fuzzy Chiton, lives in an area that stretches from Southern Florida to Panama, in the Carribean Sea. It has spines on its girdle that give it a fuzzy look, and perhaps deter predators.   It inhabits the intertidal zone, where it eats algae.

One adaptation it has is a rhythymic pattern of movement that allows it to withstand storms and rough seas.

Hamilton (1903), for example, observed a rhythmic movement of the girdle of Acanthopleura in phase with the wave period. The girdle was brought flush and tight against the substratum with each approaching wave and then was raised during the backwash. 

Peter W. Glynn, On the Ecology of the Caribbean Chitons Acanthopleura granulata Gmelin and Chiton tuberculatus Linne: Density, Mortality, Feeding, Reproduction, and Growth, SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY NUMBER 66, SMITHSONIAN INSTITUTION PRESS,  (Washington D.C., 1970), at p.5.

Another adaptation it has is the ability to tolerate a lot of sun and exposure without drying out.  (See Glynn at p. 18.)  They also exhibit "homing." that is, they move at night to feed, but return to the same area during their less active daytime hours.  (Glynn at p.7)

Their primary predators are sea stars, crabs and other crustaceans, rats, and birds.

I built a model of a chiton using aluminum tape and a large rubber band.  The plates slide to allow it to roll up.

Here is a video that shows me unrolling it.  It didn't work as smoothly as I would have liked.