Borneosa, Ng & Grinang, 2022

Key to species of Borneosa View in CoL

1a. Anterolateral margin with the epibranchial tooth distinct, sharp, separated from rest of anterolateral margin by clear cleft ( e.g., Figs. 10B View Fig , 11F, H View Fig ); male sternoplenonal cavity separated from suture between thoracic sternites 2 and 3 by narrow gap, less than combined length of thoracic sternites 1 and 2 ( e.g., Fig. 18B View Fig ) .. 2

1b. Anterolateral margin with the epibranchial tooth low to almost absent, cleft when visible, low, shallow, anterolateral margin may appear entire ( e.g., Fig. 2B View Fig ); male sternoplenonal cavity separated from suture between thoracic sternites 2 and 3 by relatively wide gap, more than combined length of thoracic sternites 1 and 2 ( e.g., Fig. 3B View Fig ) ....................................................................................... 4

2a. Outer margin of exorbital tooth distinctly serrated ( Fig. 17B View Fig ); Bulungan, Kalimantan Utara........................... B. serrata View in CoL sp. nov.

2b. Outer margin of exorbital tooth entire or almost so ( e.g., Fig. 8B View Fig ); Sarawak...................................................................................... 3

3a. Epibranchial tooth low, separated from anterolateral margin by small cleft ( Fig. 8B View Fig ); third maxilliped ischium subquadrate ( Fig. 9A View Fig ); G1 terminal segment relatively slender, long ( Fig. 21A–C View Fig ); Niah, Sarawak..................................................... B. niah View in CoL sp. nov.

3b. Epibranchial tooth strong, separated from anterolateral margin by prominent U-shaped cleft ( Figs. 10B View Fig , 11F, H View Fig ); third maxilliped ischium subrectangular ( Fig. 11A View Fig ); G1 terminal segment relatively stout, short ( Fig. 21E–G View Fig ); Bario Highlands View in CoL , Sarawak.. ............................................................................. B. bario View in CoL sp. nov.

4a. P3 dactylus distinctly more slender and elongate compared to P4 dactylus ( e.g., Fig. 5H, I View Fig ) ............................................................ 5

4b. P3 and P4 dactyli not elongate, subequal in length ( e.g., Fig. 7F, G View Fig ) ................................................................................................ 6

5a. Frontal median triangle with dorsal margin separated from lateral margins by small gap ( Fig. 2C–F View Fig ); G1 terminal segment relatively short, subcylindrical ( Fig. 20F, G, J, K View Fig ); Gunong Mulu National Park, Sarawak................. B. tenebrosa ( Holthuis, 1979) View in CoL

5b. Frontal median triangle with dorsal margin contiguous with lateral margins ( Fig. 4C–E View Fig ); G1 terminal segment very long, cylindrical ( Fig. 20M–O View Fig ); Brunei and northern Sabah ................. .................................................. B. aspera ( Ng & Stuebing, 1989) View in CoL

6a. Striae on lateral parts of dorsal surface of carapace relatively lower, rounded ( Figs. 6B View Fig , 7I View Fig ); median lobe of posterior margin of epistome acutely triangular ( Fig. 6C–E View Fig ) ....................................... ............. Barito, Kalimantan Tengah B. brachyphallus ( Ng, 2015) View in CoL

6b. Striae on lateral parts of dorsal surface of carapace strong, sharp ( Fig. 15B View Fig ); median lobe of posterior margin of epistome obtusely triangular ( e.g., Fig. 15C–E View Fig ) ...................................................... 7

7a. Epibranchial tooth small but usually visible, and even when low, demarcated from the anterolateral margin by a shallow cleft ( Figs. 12B View Fig , 14 View Fig ); G1 terminal segment with median part less distinctly bent, distal part more elongate with more tapering tip, opening small ( Fig. 22A–C, E–G View Fig ); Kapit area and upper Rejang, Sarawak............................................................................. B. kapit View in CoL sp. nov.

7b. Epibranchial tooth not visible or very low, with the anterolateral margin appearing entire ( Fig. 15B View Fig ); G1 terminal segment with median part distinctly bent, distal part ending in rounded tip with wide opening ( Fig. 22I–K View Fig ); Batang Ai National Park and Lanjak-Entimau Wildlife Sanctuary, Kanowit Basin, Sarawak................. ................................................................ B. sarawakensis View in CoL sp. nov.