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Pretty similar is Thuridilla albopustulosa which differs by the bright purple colour and the median white line on the rhinophores.
This species was posted on 13 August 2004 at these websites as Thuridilla vatae (Risbec, 1928) , Yonow (2012) made clear that this is a widespread misspelling. Let me quote:
"Risbec (1928) almost certainly named this species after the bay south of Nouméa, Baie de l’Anse Vata, of which the north-western tip is the collection locality of his single specimen, Rocher à la Voile. The suffix for commemoratives in this case is -ae, hence the spelling vataae. The original spelling is correct and should be maintained."
Nathalie Yonow, Opisthobranchs from the western Indian Ocean, with descriptions of two new species and ten new records (Mollusca, Gastropoda)
ZooKeys 197: 1-129 (22 May 2012) https://doi.org/10.3897/zookeys.197.1728
More information on Thuridilla vataae as Thuridilla vatae are on Bill Rudman's Sea-Slug Forum!
How to cite:
Köhler, E. (2017), published 23 February 2017, Thuridilla vataae (Risbec, 1928)
available from https//www.Philippine-Sea-Slugs.com/Sacoglossa/Thuridilla_vataae.htm