Key to the Indo-West Pacific species of Microprosthema

1 Carapace densely covered with numerous spines; scaphocerite narrow, oblong..................................... 2

- Carapace covered with few or no spines; scaphocerite semicircular.............................................. 4

2 First to sixth abdominal somites with rows of blunt spines...................................... M. scabricaudatum

- First to sixth abdominal somites without spines or only with rows of spines on sixth somite.......................... 3

3 Third, fourth, and fifth abdominal somites with median longitudinal carinae............................... M. validum

- Third, fourth, and fifth abdominal somites without median longitudinal carinae.......................... M. plumicorne

4 Carapace without spines; fourth pereiopod without epipod............................................ M. lubricum

- Carapace with a few small and large spines; fourth pereiopod with epipod......................................... 5

5 Sixth abdominal somite with short transverse row of spines............................................. M. fujitai

- Sixth abdominal somite without short transverse row of spines................................................. 6

6 Six or more teeth on scaphocerite; supraocular eaves concave........................................... M. takedai

- Five teeth on scaphocerite; supraocular eaves convex...................................... M. personatum sp. nov.