Subclass Streptoneura Spengel, 1881
Group of Gastropods also known under the name Prosobranchia. It are usually shelled species with a visceral torsion of 180 degrees and separate sexes. It is composed of the Superorders Archaeogastropoda, Mesogastropoda (to which the Heteropoda and Janthinidae belongs) and Neogastropoda.