Differs from all other European Cottus (except C. poecilopus) by having conspicuously tessellated pelvic-fin rays. Distinguished from C. poecilopus by possessing a single chin pore. Other characters useful to distinguish this species from other Cottus in Atlantic drainages include: caudal peduncle stout (length 14-19% SL, depth 7-9% SL and 1.5-2.4 times in its length); in prickling in adults (juveniles unknown); eye diameter 19-22 % HL; interorbital distance 0.9-1.3 times in eye diameter; last anal-fin ray with membrane connecting to body along 0.5 of its length; last dorsal-fin ray connected to body by a membrane along 0.5-1.0 of its length; membrane between pelvic fin and body on about 1/5 of last ray; membranes between pelvic-fin rays broad but narrower distally; lateral line complete 33-35+1 pores (Ref. 55856).