Box-and-whisker plots showing variation in the ratio of detached-whorl width to aperture width in some Rhiostoma species. Boxes show the median, 25th and 75th percentiles, whiskers show minimum and maximum observations, and circles show outliers. See text for the explanation of species grouping. 1 = topotype of Rhiostoma samuiense s. s. from Samui Island. 2 = topotype of “Rhiostoma chupingense” from Bukit Chuping, Malaysia. 3 = specimens of “proboscis” morphotype from Surat Thani, Thailand.