Eucocconeis laevis differs from Psammothidium rossii by having larger and often asymmetrical central areas on both valves and by wider valve ends. Psammothidium altaicum has rhomboid axial area on the rapheless valve and an elliptical symmetrical central area on raphe valve. In contrast to Eucocconeis spp., Psammothidium spp. have a convex raphe valve and concave pseudoraphe valve.
BioData Reference
Krammer and Lange-Bertalot 2/4 Pl 20 Fig 24-32