Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea) Author Ng, Peter K. L. Author Castro, Peter text Zootaxa 2016 4209 1 1 182 journal article 37321 10.11646/zootaxa.4209.1.1 2de5b7bf-3975-458a-b200-07ec69f4e013 1175-5326 272646 849BAB5C-464A-4B4A-A586-5742411EDC01 Megaesthesius westralia Davie, 2013 ( Figs. 19 M–R; 34C; 82J–M) Megaesthesius sagedae —Poore et al. 2008: 46. Not Megaesthesius sagedae Rathbun, 1909 . Megaesthesius westralia Davie, 2013: 470 , figs. 1, 2, 3A‒E [ type locality: Western Australia ]. Type material . Holotype male (3.4 × 3.8 mm ) ( NMV J54597 ), Australia , Western Australia , off Ningaloo , Southern Surveyor , stn SS10-2005, 22°04.00’S , 113°48.40'E , Sherman sled, 101-106 m , 10.12.2005 . Diagnosis . Carapace ( Fig. 19 M; Davie 2013: fig. 1A, B) subquadrate, 1.1 wider than long; front bilobed, with deep median cleft; dorsal surface with low, spherical tubercles. Lateral margins straight, parallel to each other, each with 4 teeth (last as large tubercle) separated by deep notches. Long orbits, eye peduncle elongated ( Fig. 19 O); Davie 2013: fig. 2A, B), immobile, cornea reduced, non-pigmented. Antennule greatly enlarged ( Fig. 19 N, O; Davie 2013: fig. 1), particularly in males. Third maxillipeds ( Fig. 34 C; Davie 2013: fig. 2C) nearly fill buccal cavern when closed; merus subtriangular, outer margin with small teeth; ischium subquadrate, outer margin with small teeth, about same size as merus; outer margins of merus, ischium with small spines. Chelipeds unknown. Proportionally short ambulatory legs ( Fig. 19 Q, R; Davie 2013: fig. 2D, E), dorsal, ventral margins of meri of P4 with minute teeth. Fused thoracic sternites 1, 2 ( Fig. 19 P; Davie 2013: fig. 1B, C) broadly triangular, proportionally broad, short. Male pleon ( Fig. 19 P; Davie 2013: fig. 3E) with lateral margins of somite 6, fused somites 3–5 nearly straight; postero-lateral regions slightly swollen; telson proportionally short. G1 ( Fig. 82 J–L; Davie 2013: fig. 3A– C) slender, distal segment straight, with spinules, apex slanted. G2 ( Fig. 82 M; Davie 2013: fig. 3D) nearly as long as G1, straight; slender, distal segment long, curved, as long as basal segment, directed inward. Female unknown. Remarks . This species is known only from one male specimen without chelipeds. It is apparently closest to M. yokoyai , but can be separated by a suite of carapace, ambulatory legs, male pleon, and G1 characters (see key to species of Megaesthesius ). Distribution . Known only from Western Australia . Depth: 101- 106 m .