Genus Amphithyris Thomson, 1918

Type species. Amphithyris buckmani Thomson, 1918: p. 22, pl. 15, fig. 29, pl. 16, fig. 35 (by original designation)

Diagnosis. Small shell (up to 5mm), planoconvex to biconvex, punctate, round to oval; shell outline variable depending on substrate of attachment. Ventral valve convex; dorsal valve slightly convex to almost flat; short pedicle; beak apicate; foramen amphithyrid; schizolophous lophophore. Hinge line nearly straight; triangular delthyrium; dental plates absent.