can anyone ID this? Not sure if it's harmful or not

[giants4pc]

Pictures aren't the greatest; however, they should be clear enough to give you the idea. I'm actually posting for another member who does not have a digital camera. He claims they are out in the hundreds when the lights are off. He discovered one when he got new rock and since, they seem to have multiplied. Are they destructive? They are hard as a rock and are extremely difficult to scrape off. Not sure what to do..
You can see in the first two pics that they basically blend into the rock work.
http://i24.photobucket.com/albums/c35/giants4pc/DSC00083.jpg
http://i24.photobucket.com/albums/c35/giants4pc/DSC00084.jpg

In these other two pics, it is the thing in the middle with stripes. I know the pics aren't the greatest, but you can see a bit of a tentacle of some sorts.
http://i24.photobucket.com/albums/c35/giants4pc/DSC00089.jpg
http://i24.photobucket.com/albums/c35/giants4pc/DSC00091.jpg
Any ideas?

[figuerres]

try this out:

http://en.wikipedia.org/wiki/Chiton

best guess from the photos...

[ryan115]

I agree.... chiton 100%

[giants4pc]

Pretty hard to refute that article with the pics...I guess there is no need to be worried given what it states in that article.