a href="https://www.inaturalist.org/taxa/1146541-Berthella-perforata"> https://www.inaturalist.org/taxa/1146541-Berthella-perforata
http://www.medslugs.de/E/Med/Berthella_perforata/Selection.htm
https://opistobranquis.info/en/guia/pleurobranchida/berthella-perforata/