ID please little marble eggies.

On a small piece of LR I had 3 little round shiny blackish brown marbles. They looked out of place. I do not know where they came from I added a couple pieces of LR a couple months ago. I also added some turbo snails, an emerald crab, and some blue leg crabs. It is a 20 gallon hex with two young percs, a cleaner shrimp, snails, crabs, mushrooms. Other stuff growing that I can not identify, worms, algea ect. Today I put in three pepermint shimp as I noticed aptasia anenome came with the new rock. I say eggs becsuse two have disappeared, and now there are a couple on the back of the rock. I have never seen anything anywhere like these, sooo anybody?