CLASS POLYPLACOPHORA

• CHITON SHELL

  • Markings used for identifying the group

  
• SHELL PLATES (4 LAYERS)

  1. outer, organic periostracum
  2. Inner tegmentum (made up of calcium carbonate + proteinaceous material, conchiolin)
  3. Inner articulamentum (pure CaCO3, that extends laterally to form the insertion plates of each valve)
  4. Hypostracum (innermost)
• TAXONOMIC CHARACTERS:

  1. Sculpture of the valves
  2. Granulation or spinulation of the girdle
• What is shown?

  • ANTERIOR VALVE

  
• What is shown?

  • INTERNAL STRUCTURE OF CHITON

  
• What is shown?

  • Chiton radula, coated with the hard magnetic iron mineral, magnetite
  • 17 teeth per row (for scraping and biting)

  
• What is shown?

  • AESTHETES

  
• What is shown?

  • Present in Polyplacophorans
  • Photoreceptors are their eyes
  • It is highly developed in Cephalopora