The invention concerns a lamellar clarifier (1) comprising: a) a tank (3) for liquid to be clarified (5), b) means for conveying said liquid (5) into a lower zone (9) of said tank (3), c) means (11) for evacuating said liquid (5) from an upper zone (13) of the tank (3), and d) a plurality of settling plates (Di) arranged inside said tank (3), said plates (Di) being substantially parallel and uniformly spaced apart from one another so as to define a plurality of passages (IIi) extending between said lower (9) and upper (13) zones. Said clarifier is characterized in that it further comprises tubular members (Ti) integral with said plates (Di), and oscillating fixing means (.DELTA.i) interposed between said tubular members (Ti) and said tank (3).