Buccal mass extracted from specimen 26 mm long; dorsal view. Llŷn, North Wales. March 2016.
1: each row of teeth on radula has two black major-lateral teeth permeated with extremely-hard magnetite to resist abrasion while scraping alga etc. from rock.
2: anterior rows of teeth broken off by wear; will be replaced by next teeth on radula-ribbon moving forwards.
3: less-hard golden major uncinal teeth (“sweeper teeth”) sweep up food fragments loosened by hard major-laterals.
4: hyaline shield (wide translucent anterior border of radula) overlying the supporting pink bolster cartilage. Odontophore is protruded from mouth like a tongue to operate radula when feeding.
5: complex of numerous muscle bundles which attach to valve ii for operating mouth parts and radula. Coloured by red myoglobin (oxygen carrying pigment).
Long radular sac contains growing radula; visible through translucent wall of sac;
6: radula sac pale at rear where radula formation begins.
7: major lateral teeth orange as begin to mineralize.
8: major lateral teeth darken as move forward and develop.
9: uncinal teeth acquire golden colour further forward at later phase of development.

KEY ID FEATURES and similar species at: 01 Acanthochitona crinita