Snails and slugs
See key to Mollusca families
Aquatic snails and slugs divide into two subclasses. Gill-breathing Prosobranchia are related to marine snails. Lung-breathing or secondarily gilled Pulmonata are related to land snails. Eleven prosobranch families and nine pulmonate families are recorded from Australian inland waters. They are keyed to family level in the Molluscs Key .
Identification to class Gastropoda is relatively easy, based on the snail-like shell and/or the presence of a pulmonate lung in the mantle cavity. Larvae of Helicopsychidae, a family of caddisfly (Insecta: Trichoptera) construct a helical case which resembles a snail shell, and one species was originally described as a mollusc. The trichopteran case is composed of sand grains and the animal inside is insect-like with three pairs of legs.