1	Uropod 3, outer ramus 1-articulate	2
‒	Uropod 3, outer ramus 2-articulate	9
2	Pleonites 1–3 each with dorsal tooth	M. tuberculata Nagata, 1965
‒	Pleonites 1–3 dorsally smooth	3
3	Dactylus of pereopods 3 and 4 long, feeble	M. longidactyla Hirayama, 1987
‒	Dactylus of pereopods 3 and 4 short, stout	4
4	Urosomite 2 with teeth	5
‒	Urosomite 2 without teeth	6
5	Female pereopod 6, anterior lobe of coxa shallow, weakly hooked	M. bingoensis Yamato, 1987
‒	Female pereopod 6, anterior lobe of coxa deep, strongly hooked	M. nagatai Yamato, 1987
6	Antenna 2, flagellum strongly setose	M. setiflagella Yamato, 1988
‒	Antenna 2, flagellum weakly setose	7
7	Antenna 1, accessory flagellum 4-articulate; male gnathopod 2, palm quadrate	M. koreana Stephensen, 1944
‒	Antenna 1, accessory flagellum 2-articulate; male gnathopod 2, palm oblique	8
8	Male uropod 3 outer ramus weakly arched, more than 7.0 times longer than wide; anterior lobe of coxa of female pereopod 6 as deep as coxa is, strongly hooked	M. choshigawaensis sp. n.
‒	Male uropod 3 outer ramus sublinear, about 5 times as long as wide; anterior lobe of coxa of female pereopod 6 depth less than coxal width, weakly hooked	M. shimizui (Uéno, 1940)
9	Antenna 2 flagellum strongly setose; uropod 3 outer ramus with long setae	M. quadridentata Yamato, 1990
‒	Antenna 2 flagellum weakly setose; uropod 3 outer ramus without long setae	10
10	Inferior antennal sinus absent	M. pilopropoda Hirayama, 1987
‒	Inferior antennal sinus present	11
11	Maxilla 1 palp article 1 with setae; male gnathopod 2 propodus palm oblique	M. hoshinoi Yamato, 1990
‒	Maxilla 1 palp article 1 without setae; male gnathopod 2 propodus palm quadrate	M. rylovae Bulycheva, 1955