Notarius biffi is distinguished from other EP species of Notarius by the following combination of features: a small mouth, its width 34.2–39.3% (mean 36.2%) HL; eye large, its diameter 3.8–4.5% (mean 4.2%); short mandibulary barbels, their length 10.2–13.1% (mean 11.6%) SL; short anterior internarial distance, 17.9–20.8% (mean 19.4%) HL; relatively slender caudal peduncle, depth 6.1–6.7% (mean 6.4%) SL; and gill rakers on first arch 3–4+7–8 (mode 12). The combination of the following characters also distinguish this species from other EP ariids: triangular humeral process, three pairs of barbels present, fleshy furrow between posterior nostrils absent, fleshy groove in median depression of head absent, coarse to sharp granules or spinulations on anterior surface of head shield absent, and gill rakers on rear surfaces of first two gill arches absent (Ref 54794).