Phylum Mollusca Linnaeus, 1758 - molluscs Class Gastropoda Cuvier, 1795 - snails and slugs Subclass Opisthobranchia Milne-Edwards, 1848 - opisthobranchs see Order Opisthobranchia Milne-Edwards, 1848 Order Cephalaspidea Fischer, 1883 Superfamily Runcinoidea Adams & Adams, 1854 Family Plusculidae Franc, 1968 [monotypic] 1 Genus Pluscula Marcus, 1953