Key to species of Rhachotropis from Japanese and adjacent waters 1 Head with dorsal protrusion ...................................................................................................... 2 —— Head dorsally smooth ................................................................................................................ 3 2 Pereopods 5 and 6 basis produced posteriorly .......................................................... R. aculeata —— Pereopods 5 and 6 basis not produced posteriorly .................................................... R. marinae 3 Pereonite 7 with middorsal tooth .............................................................................................. 4 —— Pereonite 7 dorsally smooth ...................................................................................................... 6 4 Pleonite 3 and urosomite 1 with middorsal tooth .................................................... R. macropus —— Pleonite 3 and urosomite 1 without middorsal tooth ................................................................. 5 5 Pereopod 5 basis not produced posteriorly. Pereopod 6 basis oval ................................ R. oculata —— Pereopod 5 basis strongly produced posteriorly. Pereopod 6 basis triangular ........................................................................................................................ R. reiwa 6 Urosomite 1 with dorsal tooth ................................................................................................... 7 —— Urosomite 1 dorsally smooth .................................................................................................... 8 7 Pereonites dorsally smooth. Telson cleft for 5% of its length ................................... R. distincta —— Pereonites with dorsal protrusion. Telson cleft for 10% of its length ................................ R. saskia 8 Eyes small, not pigmented. Telson elongate, length 3.8 times width ............................................................................................................................ R. natator —— Eyes large, pigmented. Telson not elongate, length shorter than 2 times width ................................................................................................................................ 9 9 Pereopods 5–7 basis produced posteriorly ...................................................... R. lowryi sp. nov. —— Pereopods 5–7 basis not produced posteriorly ............................................................. R. inflata

Published as part of Okazaki, Masakuni & Tomikawa, Ko, 2023, A New Species of the Genus Rhachotropis (Crustacea: Amphipoda: Eusiridae) from Japan, pp. 507-514 in Records of the Australian Museum (Rec. Aust. Mus.) (Rec. Aust. Mus.) 75 (4) on page 513, DOI: 10.3853/j.2201-4349.75.2023.1888, http://zenodo.org/record/10413640