Any ideas on these eggs?

[Joe Batt]

My tank is pest free (as far as I am aware, quarantine frags fish etc etc). I have these egg looking things on one of my rocks and wondered if anyone has an ID? There are often snails there and a sea urchin likes to hang out there too. They are around 2mm in diameter and don’t look like normal snail eggs, to me anyway.....

 

[Jay Z]

Kind of look like limpets. Are they hard to get off and solid on the top?

 

[Joe Batt]

Not prodded or tried to remove them...... just little white uniform domes

 

[KJ]

Nerite eggs!