bright yellow nubibranch (sea slug)?

[Moonrs]

I just got a nice rock with some shrooms on it from the lfs off of Bandera, and it had a hitch hiker on it. It looks like a sea slug, but I'm only basing this on pictures from my book. The book didn't show the exact one I have, and it disappeared into the LR almost right away, so I wasn't able to snap a picture . It's got a bright yellow, smooth body, and it's about 1 1/2" to 2" long. There are no other marks or bumps on it, except for the two stalks in the front. Anyone have any idea what this is, and whether I should be concerned or not?

[Instar]

There is one that is bright yellow that attacks yellow crown leathers. Once on the leather, its the exact same color and could destroy it before you find the rascal. If you don't have an id on it, put that rock in a QT until you can be sure that it only eats algae and not something you want to keep. It could eat yellow anything and may also change colors. I've seen one yellow one as a hitch hiker that ate only algae, at least when small, but, it was only 1/2 inch long. Maybe thats why some of my yellow polyps get mowed every now and then - cause the thing grew up? Without and exact id, its very risky IMO.

[Moonrs]

It's already in the tank! I haven't seen it for a couple days. Atm, I don't have any leathers...