Ellerbeckia arenaria

Drum-shaped frustules are heavily silicified and joined by valve faces in long filamentous colonies. Striae on the mantles are perpendicular to the valve faces. Areolae of adjacent striae are offset, producing a diagonal lattice pattern. Valves are of two types: Linking valves connect cells within a colony and separation valves occur at the ends of unbroken filaments. Both linking and separation valves have two complementary forms: a cameo form with ridges and an intaglio form with grooves. The interlocking ridges and grooves of linking valves extend from the valve margin to near the central region, where an irregular pattern of bumps and pits may also be present. The mantle edge on the open end of linking valves has a crenulate appearance and the connection between the valve and valvocopula looks like a zipper. In separation valves, the marginal ridges and grooves extend only a short distance in from the valve margin. Unique tubular processes are present on the mantle, which appear as simple pores that are visible in LM.

Ellerbeckia arenaria is one of only two freshwater species of Ellerbeckia recorded in the United States. The other is E. baileyi, which occurs only as a fossil in Oregon and Washington.