Grimrock

there is a room with 4 altars where you need to put specific items, I looked up which items and turns out I just need a skull and a stone to finish it. I read that there is a stone nearby, but I can't find it. I believe I've only found 1 skull through out the game and I have no idea where it is.

Is this the room you must pass to progress further, or is there another way?

God I'm lucky, I backtracked to the checkered room and I used my skull and a stone there.