Marginella is a genus of small tropical and temperate sea snails, marine gastropod molluscs in the family Marginellidae, the margin snails. It is the type genus of the family. The shells of species in this genus are rounded, smooth and glossy, with a large aperture that appears to be toothed because it shows the edge of the columellar folds. In many species the shells are colorful. The glossy surface of the shell results from the fact that the mantle covers most of the shell when the animal is active. As is typical in the Neogastropoda, the animal has a long siphon. When the animal is active, the foot extends much further out than the edge of the shell.