Key to Korean species of Protohyale (Boreohyale)

1. Gnathopod 2, male palm long, twice as long as posterior margin................................................ 2

- Gnathopod 2, male palm short, as long as posterior margin..................................................... 3

2. Gnathopod 1, propodus expanded distally, anterodistal margin with hump; gnathopod 2, palm with row of long setae and spines, not bearing truncate process near dactylus hinge; uropod 1, peduncle with long distolateral spine, length 0.46 x outer ramus.............................................................. Protohyale (B.) latimana (Hiwatari, 2003)

- Gnathopod 1, propodus, anterodistal margin slightly convex; gnathopod 2, palm with row of short and stout spines, bearing truncate process near dactylus hinge; uropod 1, peduncle with short distolateral spine, length 0.29 x outer ramus..................................................................................... P. (B.) kajiharai (Hiwatari, 2003)

3. Gnathopod 1, propodus broadly expanded, with large posterior cusp; gnathopod 2, palm with distal truncate process.................................................................. Protohyale (B.) pumila (Hiwatari & Kajihara, 1981)

- Gnathopod 1, propodus not expanded, without large posterior cusp; gnathopod 2, palm without distal truncate process.... 4

4. Gnathopod 1, propodus triangular in form, posteroproximal corner subquadrate; pereopod 7, basis ovate, posterodistal margin expanded ventrally................................................. Protohyale (B.) triangulata (Hiwatari, 2003)

- Gnathopod 1, propodus subrectangular in form, narrow, length about 2.5 width, posteroproximal corner rounded; pereopod 7, basis subovate, as long as broad, posterodistal corner weakly angulated............ Protohyale (B.) magnaocularis sp. nov.