Nudibranch and cowries

[carpetlover]

So I was collecting live rock, and I realised when I got home there were some little hitchhikers. There’s one nudibranch maybe a Hoplodoris nodulosa? Can anyone else ID and what does it eat?

also found a couple cowries, are these the reef safe kind?

 

[taricha]

looks like a pleurobranch (side gill sea slug).
pleurobranchus albiguttatus maybe.
This page says they only eat ascidians (tunicates, sea squirts)
So not a threat, but neither are they likely to be sustained in a tank.