Where are my O2 Sensors?

I'm looking for my O2 Sensors on my 2005 Lincoln Navigator. I think I found the upstream O2 sensor(in front of the Catalytic converter), but I can't find the downstream. I see what appears to be one actually ON the catalytic converter, but it doesn't look quite the same as the upstream, is that it? It seems like everything I read online says it should be after the catalytic converter and before the muffler. But the only sensor i see is actually on the converter. Any help is mucho appreciated. Thanks