Abstract
Cerataulus subangulatus Grove & Sturt and Biddulphia suborbiculata Long, Fuge & Smith have been placed in a new genus Ceratangula P.A. Sims following the observations of A. Schmidt (1888, 1890) and Long, Fuge & Smith (1946). Ceratangula is a genus with a roundly triangular valve face, three large submarginal ocelli positioned off the valve angles, an internal raised triangular area with its angles situated midway between the ocelli and, positioned within these angles, 2–3 long stout spines the external openings of rimoportulae. Cerataulus subangulatus is from the late Eocene of Oamaru, New Zealand and Biddulphia suborbiculata from the late Cretaceous, Maastrichtian of the Moreno Shale, California.
Observations on the genera Amphitetras Ehrenb., Amphipentas Ehrenb. and Diommatetras Komura are included and an evolutionary line suggested.