The cells are isolated and have a square shape when viewed from the side, with a triangular cross-section and a typically short length along their central axis. The edges of the cell walls are either straight or slightly curved with rounded corners. In each corner, there is a small projection called an “ocellus.” The area of the cell wall between these projections is either flat or slightly arched and features large, regularly spaced hexagonal patterns. These cells contain numerous chloroplasts that are small and densely packed with granules, which gives the live cells a dark coloration.