The cells are arranged in chains, connected by external tubes or strutted processes that are organized in a single marginal ring. Each cell contains two chloroplasts. These cells are short and cylindrical and form long, straight, or slightly undulated chains. The valve surface is either convex or flat. Within the ring of strutted processes or close to the center of the valve, there is a single labiate process. The spines interlock between adjacent cells. These organisms reproduce through both sexual (oogamous) and asexual means.