• Body type : Body is soft , unsegmented , Bilate rally symmetrical.
• Body parts : Body consist of head , foot, mantle and visceral mass.
• Shell : Body is protected by exoskeleton. calcareous shell secreted by mantle.
• Head : Head is distinct , bearing the mouth and provided with eyes , tentacles and other sense organs.
• Respiratory organs : Respiratory organs consist of numerous gill or ctenidia usually provided with osphradium at the base.
Lung is developed in terrestrial forms.
• Body cavity : Body cavity is haemocoel.
• Radula : pharynx contains a raspindg organ, the Radula .
• Excretory organs : Excretory organs consists of pair of metanephridia.
• Sex : Sexes usually separate (dioecious) but some are hermaphroditic.
• Fertilisation : Fertilisation is external or internal.
• Development : Development is either direct or with metamorphosis through trochophore stage.
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