Key to species and subspecies of the Odius

1. Pereonit 1 anterodorsally without peak which covers a posterior part of head. Dorsal projection of metasome 1 rounded posterodistally. The back medial tooth of epimaral plate 3 direct up ............................................................. 3

- Pereonit 1 anterodorsally with peak which covers a posterior part of head. Dorsal projection of metasome 1 acute posterodistally. The back medial tooth of epimaral plate 3 direct back and up. Odius cassigerus Gurjanova, 1972 (2)

2. Lower corner of cephalon forming acute angle. Coxa 2 rounded anterodistally. Epimeral plate 3 posterior margin with distinct acute tooth ......................................................................... Odius cassigerus cassigerus Gurjanova, 1972

- Lower corner of head subrectangular. Coxa 2 with smoothly rounded right angle anterodistally. Epimeral plate 3 with obtuse tooth medially ....................................................................................... Odius cassigerus ochoticus ssp. n.

3. Rostrum surpassing ventral margin of head. Metasome 3 with high narrow peak dorsally. Coxa 1 bluntly rounded ventrally. Propodus of pereopod 2 wide, long about 1.5 as wide. ....... Odius polarsterni (Brandt et Vassilenko, 1995)

- Rostrum does not reach ventral margin of head. metasome dorsal projection acute and upright, not narrow. Coxa 1 pointed ventrally. Propodus of pereopod 2 less wider,, long about 1.7 as wide ............. Odius carinatus (Bate, 1862)