N=8 SCFT and M Theory on AdS_4 x RP^7

We study M theory on $Ad{S}_4\times {\text{RP}}^7$ corresponding to 3 dimensional $\mathcal{N}=8$ superconformal field theory which is the strong coupling limit of 3 dimensional super Yang-Mills theory. For SU(N) theory, a wrapped M5 brane on ${\text{RP}}^5$ can be interpreted as baryon vertex. For $SO(N)\mathrm{/}Sp(2N)$ theory, by using the property of (co-)homology of ${\text{RP}}^7$, we classify various wrapping branes and consider domain walls and the baryon vertex.