Cells cylindrical, with numerous small discoid plastids, forming long chains. Complex, robust, circular valves.
Linking valve and separation valve heterovalvy, sibling cameo and intaglio valve heterovalvy.
Cameo valve with radiating ridges and stepped mantle, intaglio valve with complementary grooves and mantle without step.
Thick inner layer of valve mantle penetrated by long tubes and one or two rows of porelliportulae. Outer layer of valve mantle with channel shaped areolae, closed by vela with scattered poroids.
Valve face mostly without areolae.
Rims of linking valves with interlocking or overlapping spines. Valve mantle and valvocopula attached by crenulated edges. Cingulum usually comprised of two bands or one or two series of segmented bands. Valvocopula and bands without ligulae.