A map of collected localities of Viviparus scalateri in Iwakawa's collection  . Yellow parts show the estimated ranges, based on the label of the museum lots. Numbers indicate the sample numbers in this study (see also Table 1). Sample numbers 2964J and 2964L were collected from somewhere in Lake Biwa, but the entire Lake is not coloured to make it easier to see. Green letters and downstream of the Seta River are Lake Biwa drainage as defined in this paper. A map is created from digital national land information (Ministry of Land, Infrastructure and Transport of Japan: https://nlftp.mlit.go.jp/ksj/index.html).