Semisulcospira decipiens, S. multigranosa and S. reticulata are all endemic species in Lake Biwa and are closely related with one another. To research for an affinity among these three species, a comparison of several characteristics of radula teeth among them was made. The result indicates that S. reticulata has a short lateral, and short and slender marginals in comparison with the other two species. Furthermore, S. reticulata is significantly less in the number of cusps of both outer and inner marginals than the two others, while there is almost no difference between that of S. decipiens and of S. multigranosa. As far as the facts described above are concerned, S. reticulata seems to be departed from other two species, although it does not coincide with that based on chromosome numbers and caryotypes. Therefore, the author suggests that the affinity among these three species is still a controvertible subject.

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