Eupodiscus radiatus

Valves are circular with hexagonal areolae uniformly distributed on the valve face, 3-4 in 10 µm. The valve surface is flat or slightly concave and the central valve is not distinguished. Four (although sometimes 3-6) prominent ocelli are evenly spaced on the margin of the valve face, along a narrow ridge formed by a slightly scalloped edge. The valve face/mantle transition otherwise appears smoothly rounded. Areolae continue beyond the transition onto the mantle, where they are slightly smaller, usually 5-6 in 10 µm. Areolae are arranged in a radiate pattern from center of the valve, although they are sometimes irregularly organized. Diameter of the ocelli ranges from 3.5-10 µm and is roughly proportional to valve diameter. Rimoportulae are present at the valve/mantle transition and are interspersed between the ocelli, with one or two rimoportulae between each pair of adjacent ocelli. External openings of rimoportulae are flush with the valve face and therefore difficult to detect; on the inside of the valve rimoportulae are visible under SEM at the valve-mantle junction. The rimoportulae are small and in many specimens these are not preserved. Mantle margins are variously ornamented and often form a slight circumferential ridge.