Cell is covered by thick armoured plates; long, sharp horns protrude from both ends of the cell.
Cell ovoid, with a cluster of 3 or more short spines arising from each end.
Cell ovoid, with a long straight spine extending from each end.
Cells usually single, but may be found in loose aggregates of a few cells.
Cell is covered by thick armoured plates; if horns are present, these are short and blunt (cf. [Ceratium]).
Cells not flattened; tetrahedral or polyhedral in outline; spines arising from the corners.
Flattened cells; triangular, square, or polygonal in outline; spines often present at cell corners.