Among the teleosts three basic modes of locomotion have been recognized; anguilli-form, carangiform and ostraciiform (Breder, 1926). During the past 50 years much attention has been paid to the anguilliform (Breder, 1926; Gray, 1933 a, b; Gadd, 1952; Taylor, 1952; Lighthill, 1960, 1969, 1970) and carangiform (Breder, 1926; Gray, 1933 c; Bainbridge, 1958, 1960, 1963; Lighthill, 1969, 1970) modes. In contrast little work has been done on the ostraciiform mode. Models have been made along mechanical (Breder, 1926; Gray, 1968, p. 35) and mathematical (Smith & Stone, 1961) lines. How-ever as Gray (1968) points out, ostraciiform locomotion has not been analysed in living fish.