(Ehrenb.) D.M.Williams 1985
Meridion circulare and M. circulare var. constrictrum are asymmetric to the transapical axis.
The striae of Diatoma tenuis are less visible (higher stria density) and its costae are thinner and less silicified.
Meridion lineare has rounded ends.
(Ralfs) Brun 1880
(Grev.) C.Agardh 1831
C.Agardh 1812
D.M.Williams 1985