ice is right, percula are true clowns and Ocellaris are false clowns. I have only really seen or heard of Black and white tank bred Ocellaris, which being the same species, will work fine with regular ocellaris clowns. i advise heavily against mixing clown species, tho your most peaceful and best chance of success is likely with the percula and ocellaris.
also, I have a GSM that tried its damnedest to rip the fins off of a B+W Ocellaris. i removed the ocellaris.