C. radiatus is among the smaller Coscinodiscus species and has a box-like shape when viewed from the girdle. Its valves are notably wider than they are high. The areolae are arranged in distinct rows that radiate from the valve center, with a central rosette of slightly larger areolae. These areolae are relatively coarse compared to other Coscinodiscus species, numbering 2-4 in a 10µm span, and they are easily visible under a light microscope. The size of the areolae decreases as you move toward the valve margin. C. radiatus is a widely distributed species found in various regions.