Genus Coptothyris Jackson, 1918

Type species: Magasella adamsi Davidson, 1871.

Shells are round or transversely oval in plan, multiplicate, with rough irregular radial ribs. Pedal valve is more convex than brachial one, which can be plane and even concave. Anterior commissure is convex to pedal valve (sulcate). Hinge margin is long and slightly curved. Dental plates are strong. Middle septum in brachial valve is reduced in adults. Loop of brachial skeleton is ribbon-shaped and free.

There is a single recent species in the genus.