31a. Female, caudal ramus outer margin constricted in distal half, typical form with outer apical seta strongly outbent at base. Male, outer apical seta inbent. Male, leg 4 exopod segment 3 with two terminal spines curved.

31b. Caudal ramus outer margin usually not constricted in distal half, outer caudal seta not modified. Male, leg 4 exopod segment 3 spines not modified.