Prorocentrum clipeus cells are round, 37 - 44 long, 35 - 42 microns wide, length to width ratio 1.0-1.1. Apical area a wide rounded indentation, with a small list/collar present to the left side of the apical region. Small spine present, projecting from the apical region. Very small pores, approximately 0.1 microns diameter, present around the periphery of the valve and in short rows radiating towards the centre of the cell. Intercalary region with a horizontal banding pattern. Large yellow-brown plastid fills the cytoplasm. Large extrusomes (12 - 13 microns ) present in the anterior part of the valve, pointing towards the apical area. Nucleus large, approximately 20 microns by 10 microns , in the posterior part of the valve.
