Indochinamon bavi n. sp.

(Figs. 3 d–f, 4, 5, 6e, f)

Material examined. Holotype: male (56.8 by 42.9 mm) (ZMHU), Ba Vi National Park, Ha Tay Province, Vietnam, coll. V. Q. Nguyen, 19 Jun. 2001.

Paratypes: 2 males (46.9 by 35.8, 47.5 by 36.3 mm) (ZRC 2010.0167), same data as holotype; 1 male (49.1 by 38.6 mm) (NMNS), Ba Vi National Park, Ha Tay Province, Vietnam, coll., 3 Jul. 1998; 1 male (57.0 by 43.0 mm) (ZMHU), Ba Vi National Park, Ha Tay Province, Vietnam, a small stream at the park's main road, ca. 9.5km from park's headquarter, elevation ca. 600m, coll. Tran Anh Duc & Yuchen Ang, 11 Jun. 2010; 1 male (24.5 by 20.0 mm) (ZMHU), Ba Vi National Park, a small stream near the park's main road, at elevation ca. 450m, coll. Tran Anh Duc & Yuchen Ang, 11 Jun. 2010.

Diagnosis. Carapace (Fig. 4 a) oval, CW 1.27–1.32 times (mean 1.30, n = 4) CL, dorsal surface (Fig. 5 a) slightly convex longitudinally, transversely, regions well defined; epigastric crista distinct, oblique, postorbital crista distinct, separated from epigastric crista, externally terminated by cervical groove, anterolateral region scattered with oblique granules. Frontal to orbital margins cristate, lined with low, rounded granules, infraorbital margin (Fig. 5 a) interrupted just below external orbital angle; suborbital region smooth, without granules; subhepatic region covered with short rows of granules. External orbital angle right angled, slightly directed inwards, outer margin length about two times inner margin, outer margin cristate, lined with small granules, epibranchial tooth disconnected from outer margin of external orbital angle by short gap of crista, short, directed anteriorly; anterolateral margin moderately convex laterally, cristate, regularly lined with similar-sized granules, posterolateral margins convergent posteriorly. Posterior margin of epistome (Fig. 5 a) with three lobes, median longest, narrow, sharp, margin between median, lateral lobes composed of elongated granules.

Ischium of third maxilliped broadly rectangular exopod flagellum longer than half width of merus.

Male cheliped carpus with rugose outer surface, inner angle with sharp, long tooth, followed ventro-proximally by one to two small teeth; chela with swollen palm, scattered with low, rounded granules from outer to lower half of inner surfaces (Fig. 5 b); fingers as long as palm, straight, slightly hook-shaped distally, cutting edge regularly lined with teeth, without gap when closed. Male abdomen (Fig. 4 b) tongue-shaped, first somite with distal margin rimmed; second somite with sublateral notch on distal margin, forming rounded lateral lobes; third somite widest; sixth somite longer than telson, telson longer than width. G1 (Fig. 3 d, e) with distal third curved outwards; subterminal segment with wide convexity on proximal two-fifths of outer margin, distal part of outer margin concave, connected dorsally to shallow transverse slope; distal segment relatively stout, tip slightly directed proximally in dorsal view, dorso-outwards in anterior view, groove for G2 on dorso-lateral surface medially, on lateral surface distally, proximally, elongated opening on distal outer margin, dorsal flap (protuberance of ventral outer surface) low, slightly visible from dorsal view. G2 (Fig. 3 f) longer than G1, flagellum curving outwards, U-shaped.

Live colouration. The dorsal carapace, chelipeds, and walking legs are mostly brownish-grey. The upper half of the third maxillipeds (from the palp to the anterior part of the ischium) and the suborbital, pterygostomial, subhepatic, and subbranchial regions are a light purplish. The fingers of the chelae are reddish-brown with the tips white, and the chela is dark to light reddish-brown (Fig. 6 e, f).

Habitat and distribution. This species was collected from a mountain stream in a forested area, with a rock, sand and sometimes muddy bottom, at Ba Vi National Park in northern Vietnam. It is so far known only from its type locality.

Etymology. The new species is named after the type locality, Ba Vi National Park. The name is used as noun in apposition.

Remarks. Indochinamon bavi n. sp. can be distinguished from I. kimboiense by the characters of the chela, the carapace, and the G1. In I. bavi n. sp., the palm of the chela is only sparsely granular (Fig. 5 b), the suborbital region of the carapace lacks granules, smooth (Fig. 5 a), and the opening of the distal tip of the G1 is placed laterally (Fig. 3 d, e). In contrast, I. kimboiense has the palm of the chela densely granular (Fig. 2 b), the suborbital region of the carapace is granular (Fig. 2 a), and the distal opening of the G1 is placed on ventral surface (Figs. 3 a, b).