Himatina trophina, formerly Flabellina trophina
Hoodie Nudi Bay, Nigei Island, British Columbia
The tube on which this nudi is crawling belongs to a chaetopterid polychaete worm, either Phyllochaetopteris prolifica or Spiochaetopteris pottsi. The pronounced snout is a tubular oral veil. It may be used to suck the prey closer to the opening of the tube, and into the mouth parts of the nudi.
From Jeff Goddard, Sea Slug Forum, 2008.