former taxonomy:
Class: GASTROPODA  Cuvier, 1797
Subclass: OPISTHOBRANCHIA  Milne-Edwards, 1848
Order: ANASPIDEA  P. Fischer, 1883

on the recent taxonomy see WoRMS:
MolluscaBase (2019). Syphonota  H. Adams & A. Adams, 1854. Accessed through:
World Register of Marine Species
at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=370565 on 2019-02-28
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