This taxon has four or less septa. They tend to bend away from the valve. The valve is swollen at the center and rounded ends that sometimes bulge outward. The valves and the ends are the same width. There is a jelly pore in the center of the median inflation. It has a distinct pseudoraphe which forms a small central area. This taxon also lacks rudimentary septa(Patrick and Reimer 1966).
Diatoma fenestratum Lyngbye, Tent. Hydropht. Danicae, p. 180, pl. 61, fig. E(3). 1819.
This taxon prefers mesotrophic to eutrophic lakes and ponds. It is usually found in shallow water and seems to prefer approximately neutral water(Patrick and Reimer 1966).