Most large succineid snails belonging to the genus Novisuccinea in the Yukon have a pinkish sole and relatively pale bodies, but along the Demster Highway, from the North Fork Pass (and apparently north), snails are very dark-bodied and a dark slate-grey-blackish sole. The change from pinkish to dark soles is surprizingly abrupt, apparently at this pass, as I stumbled upon one summer at the Yukon Bioblitz. The pass is the divide between the Yukon river drainage in the south, which flows north and west to the Bering Sea, and the Mackenzie river drainage, which flows north to the Arctic. It seems likely that these two colour forms represent separate species. But, this brings into question what names should apply to the pink and dark animals. My assumption was that the pink-soled Novisuccinea is N. strigata, but that may not be the case . . .