Swamp Fingernailclam (Musculium partumeium) is a medium-sized (shell length up to 1 cm) freshwater peaclam that is distributed through much of North America, primarily east of the Rocky Mountains. In New Mexico they are only known from Road Canyon Creek, a tributary of the Dry Cimarron River, in Union County. They are found embedded in soft substrates like mud in slow-velocity waters, often ponds and swamps.