CERATANGULA GEN. NOV IS PROPOSED TOGETHER WITH A DISCUSSION ON THE GENERA CERATAULUS, EUPODISCUS, AMPHITETRAS, AMPHIPENTAS AND DIOMMATETRAS

摘要

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 raided 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 Cretaceous, Maastrichtian of the Morena Shale, California.Observations on the genera Amphitetras Ehrenb., Amphipentas Ehrenb. and Diammatetras Komura are included and an evolutionary line suggested.