(Morrow) G.Reid and D.M.Williams 2010
Semiorbis rotundus, S. eliasiae, and S. hemicyclus all have more strongly arched valves.
G.Reid and D.M.Williams 2010
Edlund, D.R.L.Burge, N.A.Andresen and VanderMeulen 2021
(Ehrenb.) R.M.Patrick in Patrick and Reimer 1966