1. Gnathopod 2 grossly enlarged, at least twice size of gnathopod 1 (males).......................................... 2
- Gnathopod 2 not larger or only a little larger than gnathopod 1 (females).......................................... 6
2. Male coxa 2 much deeper than broad...................................................................... 3
- Male coxa 2 subsquare................................................................................. 4
3. Male gnathopod 2 dactylus more than two thirds length of propodus..................... M. longicornis Chevreux, 1911
- Male gnathopod 2 dactylus very short, less than half length of propodus................... M. brevidactylus Myers, 1976
4. Male gnathopod 1 dactylus longer than propodus............................................ M. katagani sp. nov.
- Male gnathopod 1 dactylus shorter than propodus............................................................ 5
5. Male gnathopod 2 dactylus subequal in length with propodus......................... M. longidactylus Chevreux, 1925
- Male gnathopod 2 dactylus scarcely half length of propodus............................... M. cornutus Norman, 1869
6. Female uropod 2 peduncle with inter-ramal spine............................................................. 7
- Female uropod 2 peduncle lacking inter-ramal spine.......................................... M. katagani sp. nov.
7. Female ocular lobes acute..................................................... M. longidactylus Chevreux, 1925
- Female ocular lobes sub-acute........................................................................... 8
8 Ocular lobes terminating in blunt tip; antenna 2 flagellum with about 10 articles............... M. cornutus Norman, 1869
- Ocular lobes terminating in sharp point; antenna 2 flagellum with more than 15 articles............................. 9
9. Female gnathopod 2 propodus longer than carpus..................................... M. brevidactylus Myers, 1976
- Female gnathopod 2 propodus subequal with carpus.................................. M. longicornis Chevreux, 1911