Snail/Nudibranch?

My girlfriend just pointed this guy out to me about 10 minutes ago. I've never seen him before. He's been in there for at least two months, as my last addition to the tank was back in February (and that was very clearly hitch-hiker free - the next newest add was back in December).

At first I thought it was just some type of nudibranch, but when I looked closer I realized that he actually has a shell. The only type of snail I've seen that looks like this is the stomatella variety, but all the ones I've seen have been way smaller. Do they get this big? He's also got tiny filaments coming from his side (they kinda just look like spikes in the pictures). Up close, they look sort of leafy-shaped.

We watched him for a couple minutes before he disappeared back into the rockwork. He looked like he was just grazing algae off the rocks, so I'm assuming (hoping) he's harmless.

Crappy cell phone pics inc:




It doesn't look like it from the angle in the pictures, but his whole body is about as long as that hermit crabs shell (1"-ish).

Any ideas? Let him go? Pull him if I see him again? Not sure how much contact I'll have with him in the future - he's gone this long undetected.

 

Stomatella snail. Great clean up crew.

 

Excellent!

I've never seem them this large. He's actually quite cool/fun to look at.

Thanks!

 

I can't believe how fast those lil buggers move..for a snail

 

I know!

He was gone in like 10 seconds.

 

Looking more like a chiton to me.

 

I had actually considered that but, as I understand it, chitons don't really have that visible mouth/grazing mechanism that you see on snails and slugs and such. I've only seen a live chiton once, so I could be entirely wrong.

Edit: Noticed you can't really see it in the picture. He looks just like my turbo snails, without the gigantic shell. And with little frilly things growing on him.

 

+1 Stomatella snail gill and anus near head. head/mouth are on what looks like a down turned elbow noodle.

 

I've had fuzzier looking stomatellas before (just like yours) and we had a very large orange one in this tank until the cleaner shrimp got him. I was also surprised at how large the orange one got.