Genus Chasmocarcinops Alcock, 1900

Chasmocarcinops Alcock, 1900: 334 .— Tesch 1918: 280.—Balss 1957: 1661.— Serène 1964a: 264; 1968: 92 [in list].—Dai et al. 1986: 365 [in key; incorrectly as Chasmocarcinus], 387.— Dai & Yang 1991: 393 [in key; incorrectly as Chasmocarcinus], 417.—Ng et al. 2008: 76 [in list].— De Grave et al. 2009: 32 [in list].

Type species. Chasmocarcinops gelasimoides Alcock, 1900 (by monotypy, gender feminine).

Diagnosis. Carapace (Fig. 9) subtrapezoidal, high; front bilobed, with deep median cleft; anterolateral margins arcuate, with conspicuous granules particularly on anterior, posterior margins; long setae; deep, wide sulcus along each mesogastric, cardiac regions. Epistome (Fig. 23 I, J) sunken, narrow; posterior margin delimited, triangular median lobe with shallow fissure, semicircular lateral margins without visible fissures. Conspicuously raised, granular pterygostome. Orbit (Fig. 23 I, J) long; eye peduncle filling orbit, short, immobile (or sessile); cornea reduced, with reduced pigmentation. Third maxillipeds (Fig. 30 E, F) not filling buccal cavern when closed; merus elongated, narrower than ischium, anterior portion subtriangular, outer margin nearly straight, anteroexternal angle not produced; ischium elongated, about twice as long as merus. Chelipeds (Figs. 9; 40A‒D) subequal in length, with short setae except propodus of major chela of male; major chela of large males (Fig. 40 A) with conspicuously curved, thin fingers, smooth except large teeth near tips, inner surface with prominent swelling near base of fingers in large adults; fingers of minor chela (Fig. 40 B, D) subcircular in cross-section, not laterally flattened, gently tapering to tip, scissor-like, cutting margins with distinct sharp teeth; fingers of both chelipeds of female (Fig. 9 C, F, H) slender, armed with sharp (some obtuse) teeth. Inner margin of cheliped carpus smooth (Fig. 9). Ventral margins of cheliped merus of female with large tubercles. Meri of ambulatory legs (Fig. 9) with small teeth along dorsal, ventral margins, dorsal margin of male P5 unarmed; long to short setae along margins of carpi, propodi, dactyli, P5 merus, dorsal margins of P2–P4 meri. Fused thoracic sternites 1, 2 (Fig. 51 F) triangular, short; fused thoracic sternites 3, 4 (Figs. 51 F; 86F; 90F) relatively broad; semi-circular, granular ridge along middle portion of thoracic sternites 3, 4 of female. Male thoracic sternite 8 (Fig. 58 F) short, quadrate; “supplementary plate” short, longer at rounded outer margin; structures tightly appressed with most of penis concealed. Male pleon (Figs. 51 F; 58F) with lateral margins of somite 6 straight, margins of fused somites 3–5 nearly straight; telson proportionally long. G1 (Fig. 70 A–D) stout, distal segment curved, with spinules, distal segment slightly curved outwards. G2 (Fig. 70 E) about one third G1 length, slightly curved, slender, distal segment long, slightly curved. Somites of female pleon (Fig. 86 F) short, with convex lateral margins; telson proportionally elongated. Sterno-pleonal cavity of female (Fig. 90 F) moderately deep, vulvae close together in flat portion of thoracic sternite 6.

Distribution. Indo-West Pacific region: Eastern Indian and western Pacific oceans.