No interactions present.
http://www.conchsoc.org/spAccount/onchidoris-bilamellata shows how different from this are the onchidoris gills.
See instead http://www.conchsoc.org/spAccount/archidoris-pseudoargus
Any reason for thinking this is onchidoris rather than archidoris, dejay? It's quite evident that this looks very different from all the other Onchidoris b. on Ispot & conchsoc too. Just look at how small are the tubercles all over it's body in comparison to body size (in some places hard to detect); whereas in Onchidoris b. they're much larger & more prominent, + none of these tubercles are white.
See also http://www.seaslugforum.net/find/2861
If you click on the 2nd image in http://www.conchsoc.org/spAccount/onchidoris-bilamellata it gives it's size as 40cm, ie it's a full-sized animal, & note how large it's tubercles are in comparison to body size, where this one's tubercles are minute.
Yes Chris. It's rare for me not to place a comment in these posts - this keeps me alert to progress.
As it was only an agreement, for which I have no tick in Filters, then I didn't see your later comments. For some reason I had agreements in both of these - as you say it is NOT, surely, O.bilamellata and it's clever of you to notice the ragged outline, which is an helpful clue.
I have removed an agreement from one but it had no effect on Likely ID.
Lat/Lng: 55.1845, -1.5027
OS grid ref: NZ317879
rock pool filled with kelp