Frustules biraphid, aysmmetrical to the apical axis, symmetrical to the transapical axis, dorsal margin convex, smooth or undulate, ventral margin straight or concave. Raphe does not occupy much of the axial area, restricted to the ends along the valve mantle and curving slightly or strongly onto the valve face at the apices. Terminal nodules usually conspicuous. Frustules box-like or rectangular in girdle view. Raphe branches are evident in girdle view.
Cells occur singly, free, or attached by mucilaginous stalks, or in long ribbon-like colonies. The genus is widespread, but highest diversity of this species occurs in acid habitats.
Light Microscope Image(s)
Each image is accompanied by the genus and species, California Academy of Sciences slide number (ie. CAS 612010), location of the specimen on the slide, and dimension in microns.