KEY TO GUATEMALAN SPECIES OF POTAMOCARCINUS H. MILNE EDWARDS, 1853

1. Carapace with anterolateral margin bearing large, acute teeth (Fig. 1A, C); G1 with marginal process and mesodistal lobe of apex erected, not folded over apex cavity (Fig. 1 G-I); cephalic process vestigial, reduced to two low protuberances (Fig. 1I) .................................................................. Po. armatus H. Milne Edwards, 1853

1’. Carapace with anterolateral margin bearing minute, blunt teeth (Fig. 2A); G1 with marginal process and mesodistal lobe of apex folded over apex cavity (Fig. 2E, F); cephalic process bifid, with two distinct spiniform teeth (Fig. 2F) ............................................................................................................ Po. magnus (Rathbun, 1896)