3.1 Body Symmetry and Axes
3.2 Shells and Spicules
3.2.1 Comparison with Outgroups
3.2.2 Shell Geometry
3.2.2.1 The Direction of the Coil (Handedness)
3.2.3 Shell Shape and Habit
3.2.4 Gastropod Shell Orientation in Life
3.2.5 Larval Shells and Their Formation
3.2.6 Shell Formation/Secretion
3.2.6.1 Periostracum
3.2.6.2 The Role of Other Organic Compounds in Shell Formation
3.2.6.3 Shell Secretion at the Mantle Edge
3.2.6.4 Addition of Shell to the Interior of the Shell by the Dorsal Mantle
3.2.6.5 Shell Repair
3.2.6.6 Pearl Formation
3.2.7 Shell Microstructure
3.2.8 Shell Colour, Patterns, and Pigments
3.2.9 Shell Pores
3.2.10 Shell Ornament and Its Function
3.2.11 Shell Windows
3.2.12 Secondary Shell Structures
3.2.13 Agglutination
3.2.14 Other Shell Structures
3.2.15 Shell Reduction and Loss
3.2.15.1 Consequences and Opportunities
3.2.16 Growth
3.2.16.1 Shell Growth and Its Record
3.2.17 Internal Septa
3.2.18 Stable Isotopes and Trace Elements in Shells
3.2.19 Shell Resorption
3.3 The Body
3.3.1 The Epidermis
3.3.1.1 Cilia
3.3.2 Mucus
3.3.2.1 The Role of Pedal Mucus in Locomotion and Adhesion in Gastropods
3.3.3 Epithelial and Subepithelial Gland Cells
3.3.4 Modifications for Terrestrial Life
3.3.5 Acid-Secreting Tissues
3.4 Muscular Hydrostat
3.5 Attachment of the Body to the Shell
3.6 Pigments in Tissues
3.7 Non-Calcareous Structural Elements in the Body
3.7.1 Chitin – A Structural Polysaccharide
3.7.2 Cartilage – Structure and Homology
3.8 Head-Foot
3.8.1 The Head Region
3.8.2 The Foot
3.8.2.1 Pedal Glands
3.8.3 Operculum
3.9 The Mantle
3.9.1 Dorsal Mantle
3.9.2 Mantle Skirt
3.9.3 Mantle Edge
3.10 Locomotion
3.10.1 Ciliary and Muscular Locomotion Using a Creeping Foot Sole
3.10.2 Ciliary and Arrhythmic Locomotion, Including Leaping
3.10.3 Rhythmic Muscular Locomotion and Adhesion
3.10.4 Adhesion and Tenacity
3.10.5 Speed of Locomotion
3.10.6 The Effect of Substratum and Topography on the Locomotion of Gastropods
3.10.7 Correlation with Habitat
3.10.7.1 Burrowing in Soft Sediments
3.10.7.2 Burrowing in Hard Substrata
3.10.8 Bipedal Locomotion
3.10.9 Swimming
3.10.9.1 Jet Propulsion, Including ‘Flight’
3.11 Permanent Attachment to the Substratum
3.11.1 Byssal Attachment
3.11.2 Cementation
3.12 Muscles and the Muscle Systems
3.12.1 Muscle Cell Morphology
3.12.1.1 Smooth Muscle Cells
3.12.1.2 Transverse Striated Muscle Cells
3.12.1.3 Oblique Striated Muscle Cells
3.12.2 Metabolism of Contraction
3.12.2.1 Catch Muscle and Twitchin
3.12.2.2 Muscle Activation and Control
3.12.3 Some Muscular Systems in Molluscs
3.12.3.1 Retractor Muscles
3.12.3.2 Antagonistic Muscles
3.12.3.3 Body Wall Musculature
3.12.3.4 Foot (Pedal) Musculature
3.12.3.5 Shell Muscles
3.12.3.6 Adductor Muscles
3.12.3.7 Odontophoral Muscles
3.12.3.8 Specialised Hydrostatic Muscular Systems in Coleoids