Size is about a millimeter.
I've found a few of these spirals growing on my glass and on my rock. If they are snails then the most likely parent would be my Trochus snails. The ones on the glass can't be more than a week old.
There is no signs of movement, but the spirals are growing. Judging from the first photo, I think the filaments are gathering food out of the water column.
Anybody know if this is a stage of snail growth? Or is it something else entirely?
Frank