Diagnosis: Barboides britzi differs from B. gracilis in having a larger head, 26.1-30.0% of standard length vs. 22.4-26.7%; smaller eye, eye diameter 31.2-37.5% of head length vs. 39.1-44.4%; slightly longer caudal peduncle, its length 27.0-29.6% of standard length vs. 24.7-28.2%; a narrow ventromedian row of melanophores between pelvic fins and tips of cleithra vs. a wide ventromedian scattering of melanophores between pelvic fins and tips of cleithra; absence of scattered melanophores on the flanks vs. presence of scattered melanophores on the flanks; iris silvery vs. iris darkly pigmented; 1 hypural element above the 2nd hypural vs. 2 separate hypural elements above the 2nd hypural; and a yellow body colouration in life vs. an orange/red body colouration in life (Ref. 57421).

Description: Head and eye large, mouth small and subterminal, barbels absent (Ref. 57421). Nostrils single, figure-8 shaped (Ref. 57421). Circumorbital bones absent with the exception of lachrymal and supraorbital (Ref. 57421). Body elongate, dorsal fin situated mid-body, posterior half level with anterior half of anal fin; pelvic fin origin situated anterior to dorsal fin origin; caudal fin furcate (Ref. 57421). Dorsal-fin rays ii,6,i, last two articulating with same pterygiophore; anal-fin rays iii,5,i, last two articulating with same pterygiophore; principal caudal rays 9-10 + 8-9, dorsal procurrent rays 5-6, ventral procurrent rays 6; pelvic fin rays i,5; pectoral fin rays 8-10 (Ref. 57421). Lateral line absent; cephalic sensory pores absent; small transparent scales present along ventral midline, humeral region and caudal peduncle (Ref. 57421). A translucent window present in body musculature at lateral side of anterior gas bladder chamber; anterior portion of window filled in males by a large white bulbous organ, of unknown function, surrounded by fat globules; in females anterior portion of window filled by fat globules only (Ref. 57421).

Colouration: Body colourless with large black spot at caudal fin base (Ref. 57421). Other pigmentation features include: a narrow but distinct midlateral row of small melanophores along horizontal septum, starting behind operculum and continuing to caudal spot; narrow row of small melanophores along entire length of dorsal midline, from neurocranium posteriorly to caudal fin, row darkest prior to and below dorsal fin, fading to a light streak more posteriorly; dorsal area of occipital region heavily speckled with large melanophores, continuous with dorsal pigment row; dorsal surface of snout between nostrils lightly speckled with small melanophores; a thin ventromedian row of small melanophores between pelvic fins and tips of cleithra; light scattering of large dark melanophores surrounding vent and base of pelvic fins; dark row of large melanophores running along base of anal fin, continuing along base of caudal peduncle; thin streaks of small melanophores run along principle caudal fin rays and along branched rays of dorsal, anal, pectoral and pelvic fins (Ref. 57421). Pigment on dorsal surface of anterior gas bladder chamber also visible through window in body musculature (Ref. 57421). In life, body bright yellow along flanks, jaws and opercular region red; fins colourless; pigmented areas light brown in colour (Ref. 57421).