Terrathelphusa cerina n. sp.

(Figs. 5 A–H, 6A–E, 11E, F)

Material examined. Holotype: male (24.7 × 19.3 mm) (ZRC 2015.0003), damp riverbank of Sungai Sebayak, Gunung Singai, Bau, Sarawak, 1O30’17.1”N 110O10’40.1”E, 66 m asl, coll. J. Grinang et al., 31 March 2012. Paratype: 1 male (30.0 × 22.8 mm), 2 females (larger 31.0 × 26.2 mm) (ZRC 2014.0842), data same as holotype.

Diagnosis. Carapace broader than long, swollen, surface convex, very smooth; cervical grooves broad, deep; epigastric cristae high separated by deep epigastric groove; H-groove deep, long almost confluent with cervical grooves; epibranchial tooth indiscernible, anterolateral, frontal regions appearing compressed, supraorbital margin almost parallel with frontal margin; epistome median lobe blunt to pointed (Fig. 5 A–C). Male abdomen with elongated somite 6, lateral margins gently concave (Fig. 5 D). Ischium of third maxilliped rectangular, about 2.0 times maximum width (Fig. 5 E). Ambulatory legs smooth, relatively slender, second pair longest, length of fourth merus about 3.9 times width (Fig. 5 F). Cheliped carpus rugose, without granules (Fig. 5 G, H), inner angle with acutely triangular tooth; gap between fingers of major chela relatively narrow (Fig. 5 A). G1 gently curving outwards; terminal segment cone-shaped, tapered, gently curving upwards, about 0.3 times length of subterminal segment (Fig. 6 A, B, D, E). Distal segment of G2 relatively long, about 0.7 times length of basal segment (Fig. 6 C).

Life colour. Individuals are bright yellowish overall (Fig. 11 E, F).

Variation. The paratypes agree very well with the holotype male except in few non-sexual characters. The cervical grooves are proportionately broader and the ambulatory legs relatively longer in larger specimens.

Habitat. Swampy floodplains in slightly disturbed lowland primary forest. Lives in shallow burrows less than 1 m depth, with dense debris in the soil.

Etymology. The name is derived from the Greek kerinos for “yellowish wax colour”, alluding to the appearance of the species in life. The name is used as a noun in apposition.

Remarks. Terrathelphusa cerina n. sp., is distinguished from T. kuchingensis and the other three new species by a combination of characters. The carapace is relatively less swollen and convex (Fig. 5 B) than in its congeners, and the epibranchial tooth is indiscernible (Fig. 5 A–C). In comparison to its closest congener, T. kuchingensis, the G1 subterminal segment of T. cerina n. sp. is distinctly curved outwards, with the tip of the terminal segment relatively blunter (Fig. 6 A, B, D, E) (subterminal segment is less prominently curved outwards, with the terminal segment more pointed in T. kuchingensis, Fig. 2 A, B, D, E). Live specimens of T. cerina n. sp. are more similar to T. mas n. sp. but the latter species is of an even more striking yellow colour (Fig. 11 E, F, I, J).