Lost izalith/Siegmyer shortcut confusion

I went through the lost Izalith shortcut to save solaire and now idk where to go once i get to the poison maze thing. When I looked at a guide it said siegmyer should also be above the pit with the octopus things when I get there but he isnt. The last time I talked to him was at firelink when he said he was "going down below". Is there a place in the catacombs where I have to meet him first? If it matters I already beat the firesage and centipede demons.