Tellimya ferruginosa is a species of small marine bivalve mollusc in the family Montacutidae. It is found on the eastern side of the Atlantic Ocean. Bivalves are molluscs with a body compressed between two usually similar shell valves joined by an elastic ligament. There are teeth at the edge of the shell and the animal has a muscular foot, gills, siphons, mouth and gut and is surrounded by a mantle inside the shell.