2% in head length) and widely spaced rostral exsertions; pericranial rim terminating in a right-angled flange; rostral and nasal spines present from juveniles to adults; gill rakers 5-9+27-31, total 33-40 and length of filamentous barbel 31.
Both rostral and nasal spines are well-developed, retrorse and elevated.
Head narrow; perifacial rim narrow and terminating in a retrorse spine; rostral and nasal spines absent (Fig.
Perifacial rim terminating in acute-angled spine; rostral exsertions wider than interspace, often convergent; nasal spines weak or absent; chin and lip barbels prominent; filamentous barbel short, rarely reaching to eye (Fig.
Perifacial rim terminating in a right-angled or rounded flange; rostral exsertions narrow, widely spaced; nasal spines present; chin and lip barbels less bushy; filamentous barbel long, reaching to or beyond eye .
borealis reach 10 cm standard length and lack distinct postocular spines, possess a long cirrus at the base of the nasal spine
, the first or second dorsal-fin spines are not longer than the third or fourth, and the two rows of ctenoid scales below the dorsal fins extend onto the caudal peduncle (Bolin, 1936; Mecklenburg et al.