Lindavia radiosa

Cells are cylindrical with shallow mantles. The valve face is concentrically undulate, with a marginal ring of striae that occupy slightly more than one-half of the valve radius. At the center of the valve, coarse areolae of equal size are arranged in a radiate pattern. One to several areolae are scattered in the clear area at the center of the valve. The marginal striae are slightly unequal in length. Every fourth or fifth interstria, also called a costa, is thickened. These thickened costae appear in LM as shadow lines, or Schattenlinien, which number about 4 in 10 µm.

Håkansson (2002), Houk et al. (2010) and Tanaka (2007) published SEM images and written observations of this taxon, although they are not of North American specimens. External views show a concentrically undulate and radially wrinkled valve face. The slightly convex central area is surrounded by a shallow depression. Radial lines of areolae and central fultoportulae lie in grooves separated by low ridges, on which small granulae are scattered or also arranged in radial lines. At least one rimoportula opens to the outside at the end of a shortened stria. The striated marginal area consists of multiseriate striae that continue onto the mantle. Areolae in the striae are much finer than those in the central area. A ring of marginal fultoportulae occurs at the junction of the valve face and mantle.

Internally, striae are expressed as short, oblong alveoli separated by costae. The costae are sometimes divided, with every fourth or fifth costa is thickened and bearing a marginal fultoportula. The marginal fultoportula consists of a short tube with two lateral satellite pores. At least one rimoportula with is located between the central area and the marginal alveoli. The central area is concentrically undulate with areolae and several central fultoportulae arranged in radial rows. Each central areola is covered with a domed cribrum. Central fultoportulae consist of a short tube surrounded by three satellite pores.