Key to Bradycalanus, females and males

1 Head rounded; posterior Pd5 corners triangular in lateral view; Mx1 coxal endite with 5 setae.........................2

- Head crested; posterior Pd5 corners with posteroventral attenuated extension in lateral view; Mx1 coxal endite with 2 setae (male unknown)............................................................. Bradycalanus abyssicolus n. sp.

2 Female A1 short extending no more than 3 segments beyond caudal rami; P1 Re1 and 2 with outer border spines extending to base of following spine (male unknown).................................................... Bradycalanus gigas

- Female A1 long extending about 6–7 segments beyond caudal rami; P1 Re1 and 2 with outer border spines short extending well short of base of following spine......................................................................3

3 Female total length <13 mm; male right P5 Re3 inner border spine inserted opposite outer border spine, inner border with notch.............................................................................. Bradycalanus typicus

- Female total length> 14 mm; male right P5 Re3 inner border spine inserted distal to level of outer border spine insertion, inner border without notch................................................................. Bradycalanus enormis