In all these types, the teeth are affixed to the medio-ventral aspect of each pharyngeal bone. In Rutilus they are close-set and uniserial, usually five in each row. Each has a cutting edge. The two posterior teeth (4 and 5) have recurved tips, forming hook-like processes directed backwards. These teeth, together with the third, are strongly compressed, but the first two teeth are stouter and more or less conical with, pointed tips. Sometimes an additional tooth develops on the left side, a fact already noted by Hubbs and Hubbs (1944). In their discussion of 'bilateral asymmetry' in vertebrates they quote the roach (R. rutilus) as an example. Out of 104 specimens examined 79 had