The value of body ilepth varieo between 25 and 35o/o of standard length, the mean values between 28.4 and 3l.9oA, being higher in the populations from the Menam than in those from the Mekong drainage. The other proportions are shown in Table I. The species is characterized by the fact that the dorsal and ventral profiles are equally arched (almost parallel) and the mouth moderately oblique.
The difference in number of scales, anal rays, gill rakers and body
depth between the specimens from Menam (terra typ-.) and Mekong Riv.ers ."i too small as to asiribe the last ones to a distinct subspecieso P.t. lateralis;