Historical reference: Do not rely on this information. It is very old. About this collection
Nudibranchiata, a term once used for all the slug-like Gastropoda (q.v.), but which is now abandoned, as the members of it have been distributed between two separate divisions of the order Euthyneura. Thus some, such as Aplysia and Doris, belong to the sub-order Opisthobranchea (q.v.), and others, such as the slugs Arion and Umax, to the sub-order Pulmonata (q.v.).