Genus Notopelta n. gen.

Hephthopelta — Serène 1964a: 239; 1968 [in list] (part).—Ng et al. 2008: 76 [in list] (part).

Type species. Hephthopelta mortenseni Serène, 1964 (by monotypy, gender feminine).

Diagnosis. Carapace (Fig. 15 G–I) subtrapezoidal, distinctly wider than long, gently convex dorsally, 1.4 wider than long; front bilobed, with shallow median cleft; anterolateral margins arcuate, with submarginal, granular crest (Fig. 15 H), without distinct lobes or teeth. Epistome (Fig. 25 G) slightly depressed; narrow, semicircular median lobe with deep median fissure, semicircular lateral margins. Eye peduncle (Fig. 25 G) filling orbit, thick, short, granular, median part constricted, dorso-ventrally flattened (reniform appearance), mobile; cornea reduced, dorsoventrally flattened (reniform), pigmented. Third maxillipeds (Fig. 32 F) not filling buccal cavern when closed; merus ovate, outer margin salient, anteroexternal angle rounded; ischium rectangular, about as long as merus. Chelipeds (Fig. 15 G; 45A, B) subequal in length; fingers of minor chela (Fig. 45 B) subcircular in cross-section, not distinctly laterally flattened, gently tapering to tip; scissor-like, cutting margins with distinct sharp teeth; cutting margin of major chela of males (Fig. 45 A) with short, blunt teeth, largest most proximal. Ventral surface of cheliped merus with row of sharp tubercles along outer margin, inner margin unarmed (Fig. 42 L). Inner margin of cheliped carpus with short distal tooth, proximal part rounded (Fig. 15 G). Inner margin of basis-ischium of major male cheliped (Fig. 42 L) with long, conspicuous prolongation (short, triangular in small individuals). Meri of ambulatory legs (Fig. 15 G) unarmed. P5 dactylus distinctly upcurved (Fig. 15 G). Fused thoracic sternites 1, 2 (Fig. 53 F) distinctly broad, short, slightly depressed; fused sternites 3, 4 (Fig. 53 F) with broad concavity. Male pleon (Figs. 53 F, 60E) with lateral margins of somite 6 nearly straight, fused somites 3‒5 slightly concave; telson proportionally long; postero-lateral regions only slightly swollen. Sterno-pleonal cavity of male deep, press-button for pleonal holding as pointed tubercle posterior to thoracic sternal suture 4/5 near edge of sterno-pleonal cavity. Male thoracic sternite 8 long, subovate; “supplementary plate” long subovate; structures tightly appressed with most of penis concealed (Fig. 60 E). G1 (Fig. 76 F‒H) with stout basal part; distal part tapering to broad tip, with stout, long spinules. G2 (Fig. 76 I) about 3/4 length of G1; basal segment long, distal segment short. Somites of female pleon with convex lateral margins (Fig. 87 F); telson proportionally long. Sterno-pleonal cavity of female (Fig. 87 G) moderately deep, with large, ovate vulvae relatively close together, located on outer margins of cavity close to deflected suture 5/6.

Etymology. The name is derived from the arbitrary combination of notos, Greek for “back”, in reference to the conspicuously wide carapace of the type species, and pelta, which is derived from the generic name Hephthopelta to denote that that the type species was formerly included in Hephthopelta s. lato.

Remarks. The diagnostic characters for this genus are the presence of a submarginal granular crest along the anterolateral margin, a relatively wide carapace and proportionately wider male thoracic sternum, thick but dorsoventrally flattened (reniform) eyestalks and a distinct ischial prolongation of the major male cheliped. The characteristics and differences between Notopelta n. gen. and the other genera once treated as part of Hephthopelta s. lato are summarised in Table 2.

Distribution. Indo-West Pacific region: western Pacific Ocean.