Key to Megacalanidae genera, females and males

1 Exopod of P 1 in both sexes with 1,1,2 outer marginal spines; Mx2 terminal setae gently curving, extending short of mouth. 2

- Exopod of P 1 in both sexes with different arrangement of outer marginal spines; Mx2 terminal setae, curled, extending to or beyond rostrum.......................................................................................3

2 P1 basis usually with inner anterodistal hook-like processes, Mx1 Ri2 with 4 setae, Mn gnathobase with ventral tooth set at right angles to main plane of gnathobase thus appearing narrow; male right A1 ancestral segments XXII–XXIII fused................................................................................................. Megacalanus

- P1 basis without inner anterodistal hook-like process, Mx1 Ri2 with at most 2 setae, Mn gnathobase with ventral tooth set obliqely to main plane of gnathobase thus appearing broad; male right A1 ancestral segments XXI–XXIII fused.................................................................................................... Bradycalanus

3 Re of P 1 in both sexes with 0,0,2 outer marginal spines; anterior margin of head of both sexes without pair of anteriorlydirected spine-like processes but female may be crested; Mx2 terminal setae curled distally into semicircle.... Elenacalanus

- Re of P 1 in both sexes with 0,0,1 outer marginal spines; anterior head of both sexes with pair of anteriorly-directed spine-like processes or single spine-like process; Mx2 terminal setae curled completetely on themselves distally........ Bathycalanus