First Timer....what is web-thrower?

I know photos are rough. He's in a spot that my snail can't get too in a quality way of cleaning. He's little.... You're looking thru snail on glass bite marks.....

My find >>>>> It just popped up about two weeks ago. I saw it initially. It looks like a little tiny door-knob hole saw. It is white and maybe a half a centimeter wide. The white part seems to be solid and not opaque as the pics may lead. Today my wife points it out and says what is that?? I replied..."I don't know, It is something that just popped up about 2 weeks ago". She said....IT'S COOL....IT'S EATING A WEB. SAY WHAT?????? I replied. No....it is probably (dying), I assume, and shooting off "smoke" like a bubble coral that I baked with sunburn (on accident). Low and behold, I take a look and.....it is retracting a "web"....caught junk in the web....and was opening a "mouth" and dragging the webstuff back in. It was eating the web. I have been watching it for about 4 hours now....and I finally caught "it" spewing out the web.....then it reeled it back in. It seems to have no eyes, arms or even a "head" for that matter. It seems to come out of the white teethy ring....with a "top" that opens on a hinge and it seems to have grippy two things...though not teeth. If you disturb it....it pops back into the ring. Though it only raises itself a half a centimeter when web tossing. It rotates in the ring like a tank turret. It is really SMALL. I looked through 10 pages of this forum and about 10 other website forums..... WHAT IS THIS?????????

 

Most likely a vermetid snail.

 

I'm pretty sure amcarrig is correct.

Monterey Bay Aquarium: Snail (Vermetid Gastropod) Feeding Video