The cells are long and narrow, and they have a distinctive shape when viewed from the side. One end of the cell forms a large triangular structure called the footpole. The other end of the cell narrows into a needle-like structure called the headpole. The footpole is rounded or elliptical when viewed from above (valve view), and it contains one or two chloroplasts. The expanded footpole’s valve surface connects the cells together, forming long, spiraling chains. As a result, these cells are typically observed in their side view, also known as girdle view.