Tiny, round and black

[sueandherzoo]

Hi there.
My recently purchased live rock has been in tank that I set up Thursday night (3 days ago) and I've become obsessed and staring at it with magnifying glass, flashlight, etc. The very first night I spotted a tiny red worm, about the diameter of fishing line, probably an inch long. I'm assuming that's pretty common.
This afternoon, however, I spotted something that I have not seen on any of the hitchhiker threads (if it's there and I missed it I apologize). It's smaller than a pencil eraser, perfectly round, very black, and has a couple dozen "legs" or cilia around the perimeter. It moves very slowly and the legs don't move - it kind of glides along the rock.
Any ideas? It was great to see some life after my hours of watching but it sure doesn't look pretty!
Thanks in advance.

 

[valgae]

picture?

 

[cranberry]

Could it be a scutus?

 

[sueandherzoo]

I've tried getting photos of it but still being so new I haven't mastered how to hold a flashlight, hold a magnifying glass, and hold a digital camera. He moves slowly enough that I could turn the tank light on and photo him except his favorite spot seems to be on the underside of a piece of living rock, so I really need to shine a light on him to see him clearly.
I looked up scutus and observed some photos and that's close, but I don't think so. This guy is perfectly round, has little "fringe" all around the circle, has no white on him, and does not have any antenna. I'm not seeing things.... I've spotted him several times now. I've tried searching Google but it's hard when you really don't have any terminology to besides marine+round+black.

 

[spanko]

Could it be an Urchin?

 

[cranberry]

Try to get a really bad pic? Maybe someone will recognize the outline so our guesses could have a little direction.

 

[cranberry]

As for the little red worm.... did it have bristles going through the substrate/LR or did it look more like this....?

 

[sueandherzoo]

Yes, by George - I think you're onto something! I just Googled sea urchins and I think that's what it is! Since it's so tiny and since I'm only seeing it from the top down I'm only distinguishing this "fringe" around the edges but it could very well have "fringe" all over. Plus it's so black that it's hard to distinguish anything on it's body - I only see the tiny flecks of spikes against the contrast of the rock he's on.
And even though I understand and appreciate the suggestion of posting a photo, even a bad one, I had to laugh. I think I can provide that.

Off to go read about urchins.
Thanks!

 

[sueandherzoo]

The red worm did not have bristles, looked perfectly smooth. Of course it could have had some white or translucent stuff (real technical term, huh?) hanging off of it but it was too tiny for me to tell. I had spotted him BEFORE I dug up my magnifying glass.

 

[spanko]