the formerly Order NOTASPIDEA  Fischer, P., 1883 is splitted:

Class: Gastropoda   Cuvier, 1797 
Subclass:  Heterobranchia Gray J.E., 1840
Clade: Euthyneura Spengel, 1881
Clade: Euopisthobranchia Jörger et al., 2010
Superfamily:  Umbraculoidea  Dall, 1889 (1827)

Class: Gastropoda   Cuvier, 1797 
Subclass:  Heterobranchia Gray J.E., 1840
Clade: Euthyneura Spengel, 1881
Clade: Nudipleura Wägele & Willan, 2000
Subclade: Pleurobranchomorpha Schmekel, 1985 
Superfamily: Pleurobranchoidea   Gray, 1827 
Family: Pleurobranchidae  Gray, 1827 

Berthella plumula

Pleurobranchus membranaceus