It's really hard to tell from that picture. Are they hard and stuck on the glass? Kind of spiral a little? If so I'd say spirorbid worms. They're filter feeders that form a small shell to live in. My snails just hatched eggs and all the eggs were buried slightly in the sand bed, so if it's on the glass I don't think they're eggs. They look too big to be amphipods but too small to be copepods. Look up spirorbid worms on google and see if that matches what you have.