Melosira moniliformis cells typically have a wider width compared to their height, giving them a subcylindrical shape. These cells are organized into chain-like structures resembling beads, held together by mucilage pads. The development of linking spines is limited. Occasionally, cells are connected in pairs or groups of three by their girdles. The valve surface is flat and features small spines or granules. The mantle runs parallel to the pervalvar axis, with a slight curvature towards the valve surface, and a collar is absent. Labiate processes are distributed across the entire valve surface but are more concentrated on the valve face and the mantle edge. The chloroplasts within the cells are irregularly lobed and disc-shaped, positioned in the peripheral cytoplasm.