Etymology. Worrell (1961: 27) provided no derivation of name, but it is presumably from Latin naris meaning the nostrils, or more broadly a snout described in diagnosis by Worrell as “elongate with a large posteriorly acute rostral”, and from Greek ophis meaning snake. Since ophis is a masculine noun the spelling of bimaculatus does not change.

Revised diagnosis. A monotypic genus comprising N. bimaculatus, a small, very slender fossorial hydrophiine elapid snake (total length to 468 mm this study, males mean 335 mm, females 354 mm, tail length 6.0‒12.1% of SVL mean 8.6%) with: head narrow, depressed and not distinct from neck; protrusive round-shaped snout without cutting edge; no canthus rostralis; frontal not much wider than long; internasals present slightly smaller than prefrontals, suture between internasal and prefrontal slightly to moderately oblique; preocular in contact with nasal, rarely separated by prefrontal; typically upper primary and secondary temporals fused to form a single elongate scale without deep ventral descent (Fig. 3A), occasionally 1 + 1; rostral as slightly wider than high, posteriorly acute and projecting deeply between internasals; a consistent colour pattern of dark transverse band extends across nape and dark broad band across head forward to level of eyes; tip of snout occasionally dark; variable body colour of shades of reddish, yellowish, orange brown or bright red often with darker margins on posterior facets and pale base forming reticulated pattern; 178‒234 ventrals; 184‒242 vertebrals; midbody scales very glossy and smooth, in 15 rows occasionally increasing to 16 posterior to the head and decreasing to 14 (rarely 13) anterior to the vent; anal and 18‒33 subcaudals divided; supralabials five, last very large possibly through fusion of lower primary temporal with fifth and sixth supralabials; infralabials seven; ventral surface white with glossy shine; eyes are small with pupils indiscernible within black irises (Bush 2017). Other features in the genus are the reversion to the primitive karyotype of 2N = 36 (16M and 20m) (Mengden 1985), and pterygoid tooth row reduced posteriorly such that it does not extend beyond the level of the ectopterygoid-pterygoid articulation (Greer 1997).

Most similar to the monotypic genus Neelaps in general aspects of morphology and scalation (including cranial, dentition, and hemipenial morphology, Scanlon 1985; Keogh 1999) differs in:

• Larger adult ToL to 468 mm (versus to 271 mm) and more slender-bodied indicated by 40% higher IBR values (Table 2), while absolute BW and BD is on average 2.9% and 1.8% narrower.
• Proportionately shorter HeadL and SnL, HeadL 2.2% of SVL (versus 3.4%) and SnL 0.8% of SVL (versus 1.2%).
• TailL typically ˂ 12% of SVL (versus TailL typically > 10% of SVL).
• Rostral as high as wide posteriorly acute and projecting deeply between internasals, Fig. 3A (versus rostral much wider than high posteriorly obtuse and only slightly projecting between internasals, Fig. 3B).
• Suture between internasal and prefrontal oblique, Fig. 3A (versus suture between internasal and prefrontal transverse, Fig. 3B).
• Much higher ventral and vertebral scale counts of 178‒234 and 184‒242 (versus 124‒145 and 128‒148).
• Typically five supralabials, Fig. 3A (versus typically six supralabials, Fig. 3B).
• Typically extent of the dark head band not behind parietals (except in eastern parts of range in Western Australia), Fig. 3A (versus typically behind parietals to partially or completely cover first vertebral, Fig. 3B).
• Dark band on nape transverse, Figs. 5A, B, C, D (versus dark band on nape crescent-shaped, Figs. 7A, B, C, D).
• Tip of snout occasionally dark and often extending on to ventral edge of rostral (versus tip of snout consistently dark and not extending on to ventral edge of rostral).
• Without obvious pattern along the body (versus typically vertebral stripe present along the body, or if reduced some indications remain, unstriped individuals share a superficial resemblance).

Based on phylogenetic affinities, Narophis is compared with the other fossorial snake genera of Antaioserpens, Brachyurophis and Simoselaps using Storr et al. 2002; Cogger 2014; Couper et al. 2016 and Wilson & Swan 2021.

Differs from Antaioserpens in: larger adult ToL to 468 mm (versus to 438 mm), more slender body form (versus moderately robust), higher ventral and subcaudal scale counts of 178‒234 and 18‒33 (versus < 159 and < 22), typically one elongate temporal scale (versus 2 + 2), protrusive round-shaped snout (versus protrusive weakly wedge-shaped snout), five supralabials (versus six supralabials), preocular in contact with nasal, rarely separated by prefrontal (versus preocular and nasal separated by prefrontal) and widely allopatric distributions.

Differs from Brachyurophis in: larger adult ToL to 468 mm (versus to 390 mm), more slender body form (versus moderately robust), higher ventral scale counts of 178‒234 (versus < 190), typically one elongate temporal scale (versus typically 1 + 1, but often fused in B. semifasciatus), protrusive round-shaped snout without cutting edge (versus protrusive wedge-shaped snout with transverse weak to strong cutting edge) and without obvious pattern along the body (versus except B. incinctus (Storr, 1968) and B. morrisi (Horner, 1998) cross-banded along the body, but bands ragged-edged in B. fasciolatus). Additionally, Narophis feed on small lizards, while most Brachyurophis species feed entirely on reptile eggs, having highly modified dentition to accommodate this oophagous diet.

Differs from Simoselaps in: larger adult ToL to 468 mm (versus to 390 mm), more slender body form (versus moderately robust), higher ventral scale counts of 178‒234 (versus < 135), typically one elongate temporal scale (versus 1 + 1, but primary temporal fused with second last supralabial in S. anomalus and primary temporal often large contacting oral margin in S. littoralis (Storr, 1968) and without bands along the body (versus except S. minimus encircled by bands along the body).