Ventral face (articulamentum) of disarticulated valves. Sublittoral, Orkney. February 2015. Leg. P. Lightfoot per J. Porter.
Apophyses (1) extend under the next valve forwards and leave a scar of similar shape on it (2) when the connecting muscle is removed.
[It is difficult to cut away the muscle without breaking the apophyses on freshly dead chitons. They can be disarticulated without damage to the valves by standing them in shallow 10% NaOH overnight. CAUTION; extremely caustic, burns skin and seriously damages eyes. Or, keep in preservative for some time until the muscle weakens and then pull the valves out with strong forceps.]

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