Psammothidium scoticum differs from P. daonense and P. ventralis by its linear-elliptical shape. Valves of P. daonense are larger and elliptical, while valves of P. ventralis are more gibbous with wide subrostrate to subcapitate ends. P. acidoclinatum differs from P. scoticum by its wider axial area on rapheless valve and elliptical-lanceolate valve shape. Both P. acidoclinatum and P. ventralis have lower striae density than P. scoticum.
BioData Reference
Krammer and Lange-Bertalot 2/4 Pl 24 Fig 8-22