Key to species of the genus Platyscelus Bate, 1861

1. Gnathopod 1; propodus with serrated anterior margin...................................... P. ovoides (Risso, 1816)

- Gnathopod 1; propodus with smooth anterior margin.......................................................... 2

2. Gnathopod 1; carpal process short, not reaching mid-length of propodus. Pereopod 5; basis with undulated anterior margin. Pereopod 6; basis with proximal and distal notch on anterior margin....................... P. crustulatus (Claus, 1879)

- Gnathopod 1; carpal process almost as long as propodus. Pereopod 5; basis with smooth anterior margin. Pereopod 6; basis without notches on anterior margin........................................................................ 3

3. Gnathopod 1 almost sub-chelate. Pereopod 5; coxa with lateral knob, or spiniform process (not developed in juveniles). Pereopod 6; basis with relatively small fissure, only half as long as merus.......................... P. armatus (Claus, 1879)

- Gnathopod 1 distinctly chelate. Pereopod 5; coxa without lateral process. Pereopod 6; basis with relatively large fissure, about equal in length to merus.......................................................... P. serratulus Stebbing, 1888