former taxonomy:
Class: GASTROPODA  Cuvier, 1797
Subclass: OPISTHOBRANCHIA  Milne-Edwards, 1848
Order: SACOGLOSSA  von Ihering, 1876

on the recent taxonomy see WoRMS:
MolluscaBase (2019). Mourgona  Er. Marcus & Ev. Marcus, 1970. Accessed through: World Register of Marine Species
at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=415656 on 2019-07-25
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