We present the results of an extensive light-(LM) and scanning electron microscope (SEM) study of internally costate pseudocellate multipolar diatoms previously placed within Biddulphia, Entogonia, Sheshukovia and Triceratium. For the first time, we critically examine the poorly known genus Sheshukovia. We find that the separation of Sheshukovia from Triceratium is justified, as advocated by Gleser (1975, 1984), but also show that Sheshukovia as circumscribed by Gleser (1975, 1984) is a heterogenous taxon comprising at least three morphologically distinct groups. In order to clarify the confused taxonomy of pseudocellate multipolar diatoms, a preliminary phylogenetic analysis is presented, including Triceratium, Sheshukovia, Entogonia, Medlinia and two new closely related genera proposed here: Entogoniopsis and Trilamina. Both new genera have valvocopulae that attach to costae on the valve interior by means of a variety of clasping devices. Entogoniopsisis is characterized by areolate valves and a twofold mec