Key to species of Microtopsis

1. Dorsal surface of carapace relatively smooth (Fig. 18 A). Anterior part of lateral carapace margin with low granules (Fig. 18 A). Male telson relatively semicircular (Fig. 80 B). G1 is proportionately short, median twist weakly pronounced, tip gently hooked (Fig. 81 A‒E) [Japan]........................................................................... M. takedai

- Dorsal surface of carapace covered with distinct small granules (Fig. 18 B, C). Anterior part of lateral carapace margin with short spiniform granules (Fig. 18 B, C). Male telson triangular in shape (Fig. 80 F). G1 proportionately long, with strong median twist, tip distinctly hook-shaped (Fig. 81 G‒L) [Indonesia].......................................... M. teschi n. sp.