The cells are lengthy cylinders with a circular cross-section, forming loosely connected and fragile chains. These cells can be considerably longer than they are wide, or they may appear roughly rectangular when viewed from the side. The segments in the girdle region have a smooth surface and are challenging to distinguish under light microscopy. The valves are slightly convex and feature a small oblique process near the center, which fits into a small depression on the adjacent cell. These cells contain numerous small, plate-like chloroplasts, and the nucleus is situated close to the cell wall.