1. Eyestalk extremely long, 0.3 or more of carapace breadth.......................................... Euphylax dovii

– Eyestalk not as long, much less than 0.3 of carapace breadth................................................... 2

2. Carapace narrow, 5 anterolateral teeth; pereopods 5 without flattened swimming paddles................ Carcinus maenas

– Carapace broad, 9 anterolateral teeth, pereopods 5 with flattened swimming paddles................................ 3

3. Male abdomen triangular; anteroexternal angle of merus of third maxilliped not strongly produced laterally...................................................................................................... Portunus xantusii

– Male abdomen shaped like inverted T; anterolateral angle of merus of third maxilliped strongly produced laterally............................................................................................. Callinectes arcuatus