The cells are connected through mucilage pads at their tips, forming star-shaped and zigzag-like colonies. These cells are needle-shaped, often elongated, twisted, and occasionally bent. They can exist either individually or as part of different types of colonies. The central part of the cell is generally broad and sometimes varies in width along the length of the cell. The areolae on the cell surface can be circular or elongated in a transapical direction. Each cell has one labiate process at each end, with the apical spine typically present at one or both ends. There are no apical fields, and the presence or absence of marginal spines can vary. Small chloroplasts are scattered throughout the cell.