Among other cestodes collected by me some years ago were specimens of the prismatic malformation of a tape-worm which I have recently examined. This abnormality in the taenioid group of cestodes has been frequently reported in Europe, especially in Taenia saginata, since Andry's case was first described in 1700. This malformation is known as Taenia ‘tridre,’ ‘triquestre,’ or ‘prismatique’ in French; as ‘dreikantige’ in German, and as ‘tri-radiate’ or ‘prismatic’ in English. But as far as my knowledge goes, we do not find a full description of any such abnormality in Taenia crassicollis, though a brief description of it was given by Bremser in 1819 and 1824. It is now recorded for the first time from Japan.