The Snuffbox has disappeared from roughly 60 percent of the rivers and streams it once occupied in North America. Its surviving populations are fairly small and isolated. Today, the species is limited in Canada to a 50 km reach of the East Sydenham River and an unknown portion of the Ausable River. It prefers shallow depths and swift-moving clear water, and like many mussels, buries itself in the substrate.

The Snuffbox has a thick, solid shell that is triangular in males and inflated in females. Male Snuffbox grow to lengths of 70 millimetres; females to 60 millimetres. The raised part at the top of the shell-called the beak-is swollen and sculptured with three or four faint double-looped ridges. The shell is rounded at both ends; its colour is yellowish to yellow-green and marked with numerous dark green rays that are often broken into triangular spots. The elongated teeth along the inside of the hinge are short and straight, raised and notched: there are two on the left side and one on the right. The Snuffbox enjoys a relatively long life-about ten years. The Snuffbox is sexually dimorphic, meaning that males and females have distinctly different physical characteristics.