Unio Pictorum is a species of aquatic bivalve mollusc The shell is narrow and elongated, reaching up to 145 mm in length. The upper and lower margins of the shell are almost parallel. The colour is from yellow-olive in young species to brown-green in older molluscs. The species can move over the pond floor by using their white foot as anchor. The movement is very slow, leaving a characteristic trail.
The species inhabits rivers and lakes, but it is not abundant in water of strong current or in silty water bodies. It is common throughout Eurasia, except the North and Northeast.
The mollusc can typically be found at depths ranging from several centimetres to several metres. It prefers sandy, soddy or clay water beds, and is less common on more soddy water beds. The species feeds mainly on detritus, plant and zoo-plankton.