Morphologically, identification of small Rhodeus species has been difficult, especially differentiation of small-sized specimens of R. sinensis from bitterlings having 46 diploid chromosomes such as R. atremius, R. fangi, and R. notatus. Both R. sinensis having 2n=48 and small bitterlings having 2n=46 are frequently collected together, and share similar meristic characters and body form. Accordingly, museum collections in China have frequently been misidentified. For example, a figure of the female R. fangi in Lin (1998: 452, fig. 256) is not R. fangi but R. sinensis. As the cephalic sensory canal system of R. sinensis (Type III) is very different from that of bitterlings having 2n=46 (Type I), they can be identified clearly by examination of cephalic sensory canals (Fig. 1).